摘要:

The release of prolactin (PRL) from a clonal cell‐line of anterior pituitary cells (GH4C1) was inhibited by somatostatin (SRIH) in a dose‐dependent manner (ED50nM). The inhibition (20% of control levels) was detectable within 50 s and maximal within 90 s. Thyroliberin (TRH) enhancement of PRL secretion was biphasic. SRIH inhibited both phases equally. Ionomycin in combination with the phorbol ester, TPA, mimics the TRH‐elicited PRL release, and SRIH partly inhibited this effect. SRIH had no effect on TRH‐stimulated formation of inositol trisphosphate, and only small effects on TRH‐activated adenylate cyclase. Vasoactive intestinal peptide (VIP) and forskolin stimulated cAMP formation and PRL release potently. SRIH inhibited both effects of VIP and forskolin, and there was a close correlation between the inhibition of PRL secretion and cAMP accumulation. 8‐Bromo‐cAMP enhanced PRL release, an effect that was also partly reduced by SRIH. The Ca2+channel activator, BAY‐K‐8644 and high extracellular K+increased PRL release, and SRIH caused a partial reduction in the release response to both secretagogues. SRIH lowered [Ca2+]1, and markedly reduced the rise in [Ca2+]1elicited by TRH, VIP and K+. SRIH did not influence the Ca2+spikes recorded in Na+‐free solution, and had no effect on the TRH‐induced membrane potential changes.Ourresults demonstrate that SRIH may inhibit PRL release from GH4C1cells by (1) inhibiting hormone‐sensitive adenylate cyclase, (2) blocking the effect of cAMP and (3) lowering [Ca2+]1. None of these effects is, however, sufficient to explain all the effects of SRIH, suggesting that SRIH also exerts a major action at a step subsequent to cAMP accumulation and [Ca2+]1elevation. Since the GH4C1cells possess one single class of binding sites, this implies that the same SRIH receptor is coupled to several cell

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08408.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The nonapeptide i‐deamino‐cysteine‐8‐D‐arginine vasopressin (dDAVP) was gavage‐fed together with cow's milk whey protein to young, developing rats. The transepithelial passage of dDAVP in the gastrointestinal (GI) tract was assessed by a specific RIA as immunoreactive levels in blood serum extracts and as urinary excretion of dDAVP 0.5–8 h after feeding. In 14‐day‐old rats the passage of dDAVP was higher than in 30‐day‐old rats, since the 14‐day‐old rats had significantly higher serum levels (5–10 times) 0.5‐2 h after feeding and a urinary excretion approaching 0.15% of the administered amount after 8 h. In the 30‐day‐old rats urinary excretion increased up to 0.05 % after 2 h and then levelled off. It was also clear that 30‐day‐old rats had a slower transfer to and faster elimination from serum than 14‐day‐old rats. dDAVP appeared to be passed over the GI tract mucosa independently of intestinal proteolysis since feeding it to 30‐day‐old rats together with the proteinase inhibitors, soya‐bean trypsin inhibitor and pepstatin did not influence the serum or urinary levels. Thus, dDAVP was taken up from the GI tract into the blood circulation and excreted in the urine of young rats. The decrease in the passage of dDAVP found around weaning appears to be related to developmental processes affecting the permeability of the intestina

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08409.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The effect of sympathetic nerve stimulation and intra‐arterial infusion of neuropeptide Y (NPY) on net fluid secretion and release of vasoactive intestinal polypeptide (VIP) was studied in the cat small intestine during a secretion due to cholera toxin. Activation of the splanchnic nerves (4 Hz, 5 ms, 5 V) decreased net fluid secretion to 57 ± 10% of control. Concomitantly, the release of VIP was reduced to less than 50 %. Furthermore, close i.a. infusion of NPY (estimated increase in plasma concentration 75 nmol l‐l) reduced the net fluid secretion and VIP release to 27 ± 5 and 28 ± 4% of the pre‐stimulatory value. The correlation between the decrease in net fluid secretion and reduction in VIP release showed a strong positive correlation (r= 0.83). These results strongly indicate that the antisecretory effect of sympathetic nerve stimulation during cholera diarrhoea is mediated by inhibition of secretory VIP neurons in the intestinal mucosa. A similar mechanism is also proposed for the intravascularly administ

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08410.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The haemodynamic effects of endurance training with or without anabolic steroid treatment (nandrolone decanoate, 5.0 mg kg‐1week‐1) were studied before and after a six‐week sedentary period in anaesthetized, open‐chest rats during isoproterenol and CaCl2loads. In comparison to the control group (CG I,n= 13) endurance training (TG I,n= 10) increased the resting stroke index significantly, end‐diastolic pressure and during CaCl2infusion the end‐diastolic and end‐systolic volumes. Peripheral resistance decreased in TG I during both inotropic loads but increased in CG I (P<0.01 between the groups). After combined endurance training and anabolic steroid treatment (TSG I,n= 16) the haemodynamic state was similar to that in CG I except peripheral resistance which was even higher than in CG I. The heart weight to body weight ratio was significantly greater both in TG I and TSG I than in CG I. After a six‐week deconditioning period the haemodynamic values were essentially similar in endurance trained (TG II,n= 10) and in control rats (CG II,n= 12). After the sedentary period, in the simultaneously trained and anabolic steroid‐treated group (TSG II,n= 13) stroke index and end‐diastolic volume decreased more during isoproterenol load when compared with TG II or CG II (P<0.05 between the groups). Peripheral resistance was higher in the TSG II than in the two other groups. In conclusion, the enhanced pumping performance of the heart by increased left ventricular diastolic filling after endurance training is attenuated by simultaneous anabolic steroid treatment which further increases the peripheral resistance. Detraining reversed the main training effects in six weeks and simultaneous anabolic steroid treatment led to a decreased left ventricular filling and to elevated peripheral resistance after t

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08411.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The haemodynamic effects of endurance training and physical deconditioning were studied in anaesthetized rats using aortic and left ventricular pressure recordings and volume measurements by thermodilution method during isoproterenol and CaCl2loads. The resting stroke volume was significantly larger in the training group (TG I,n= 10) than in the control group (CG I,n= 13). During the CaCl2infusion stroke index, end‐diastolic and end‐systolic volumes increased in the TG I, but decreased in the CG I. Both isoproterenol and CaCl2decreased systemic vascular resistance in the TG I, but increased it in the CG I. After a six‐week deconditioning following training period (TG II,n= 10) stroke index, end‐diastolic and end‐systolic volumes decreased during CaCl2and isoproterenol infusions similarly to the control deconditioning group (CG II,n= 12). These responses differed significantly from those observed in the TG I. Peripheral resistance increased in both the CG II and the TG II. Cardiac hypertrophy observed during training was partly reversed after the deconditioning period. In conclusion, endurance training improves the pumping performance of the rat heart by enhancing the diastolic filling of the left ventricle and decreasing peripheral resistance during inotropic load. Left ventricular contractility is not affected. A six‐week deconditioning period after endurance training returns the haemodynamic changes to seden

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08412.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

In anaesthetized open‐chest pigs (n= 15) we examined whether myocardial oxygen consumption (M Vo2) per min increased in proportion to heart rate during right atrial pacing at control, high and low inotropy. By modulating aortic constriction and the circulating blood volume, left ventricular (LV) systolic blood pressure, stroke volume andLVdimensions were kept constant. Examinations at control inotropy (n= 7) showed a linear relationship between increments inMVo2beat‐1andLVdP/dtwhen heart rate was increased in four steps, each of 10 beats min‐1from 130 ± 3 beats min‐1(r =0.76 ± 0.08). In a second series (n= 8) heart rate was increased by 36–37 beats min‐1in control experiments, during intracoronary isoproterenol infusion (high inotropy) and after propranolol administration (low inotropy). The increments inMVo2min‐1during pacing tachycardia were not significantly different at control, high or low inotropy. At high inotropyMVo2beat‐1andLVdP/dtdid not rise significantly during pacing tachycardia. Myocardial oxygen consumption beat‐1increased more at control (6.3 ± 2.0%) than at high inotropy (diflf:P<0.02). At low inotropy MVo2beat‐1increased even more (17.4 ± 2.8%) than at control inotropy (diff:P<0.05). Thus, the increase inMVo2beat‐1during pacing tachycardia is related to the increase inLVdP/ dtand is dependent on the level of inotropy; great increments during tachycardia after propranolol administration and no changes during intracorona

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08413.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The effect of angiotensin II‐induced hypertension on selected biochemical parameters was studied in Sprague‐Dawley rats. Angiotensin II infusion at rates of 41.7 μg h‐1kg‐1and 12.5 μg h‐1kg‐1for 2, 5, 10 and 15 days elevated the systolic blood pressure from 143 ± 7 mmHg to 215–230 mmHg (P<0.001) and 185–195 mmHg (P<0.001), respectively. The left ventricular weight/body weight ratio increased 10–14% (P<0.05) and 23–32% (P<0.001) after 2–15 days in rats treated at the lower and higher infusion rates, respectively. Prolyl 4‐hydroxylase (PH) activity, a marker of collagen synthesis, was evenly distributed in the left ventricle. PH activity increased by about 100% in both subendocardial and subepicardial layers of the left ventricular wall after angiotensin II infusion for 10 days at 41.7 γ h‐1kg‐1, but remained unaltered at 12.5 μg h‐1kg‐1. No change was observed in hydroxyproline concentration. Myosin isoenzymes (V1‐V3), which reflect myocardial contractility, were unevenly distributed in the left ventricular wall: the proportion of the fast‐turnover isoenzyme (V1) was smaller in the subendocardial layer than in the subepicardial layer. The proportion ofVldecreased after treatment in both layers. Alkaline phosphatase activity, a marker of capillary density, was evenly distributed transmurally in the left ventricular wall. Angiotensin II caused a slight decrease in this activity in both myocardial layers. The results suggest that the elevation of blood pressure leads to transmurally evenly distributed changes in biochemical parameters reflecting collagen synthesis, capillary density and

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08414.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Capillary permeability of [14C]inulin and [51Cr]EDTA was examined in human forearm in five healthy, subjects by indicator diffusion technique. Injections of, initially [125I]albumin and [14C]inulin, and after 30 min resting, of [125I]albumin and [51Cr]EDTA, were given in a brachial artery. During light exercise of the forearm, blood was sampled in 2‐s periods from a deep cubital vein primarily draining muscles. The plasma flow rate, calculated as the dose of [125I]albumin in the injectate divided by the area under the curve for the venous concentration of125I, was, on average, 8.5 ml min‐1100 g‐1forearm. Assuming [125I]albumin is a partially permeable tracer, a correction for extraction of albumin was performed. This gave extraction fractions of 0.107 ± 0.015 (mean ± SEM) for [14C]inulin and 0.377 ± 0.033 for [51Cr]EDTA, respectively. The capillary permeability surface area product per 100 g tissue (CDC) was for [14C]inulin 0.90 ± 0.19, and for [51Cr]EDTA 3.31 ± 0.38 ml min‐1100 g‐1forearm. The average of the ratios of the CDC values of [51Cr]EDTA to those of [14C]inulin, 4.0 ± 0.5, is significantly higher than the corresponding ratio between the measured free diffusion coefficients in water at 37 ±C, 3.07 ± 0.002 (N= 36 and 17, respectively). This indicates that there is some degree of restriction for [14C]inulin (MW 5200) relative to [51Cr]EDTA (MW 340.2) and it points to an ‘equivalent pore radius estimate’ of about 160 Å in hu

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08415.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

The mechanisms of adaptation of the trunk to changed mechanical conditions were studied during locomotion in man. The myoelectrical (EMG) activity in lumbar back muscles and the movements of the trunk were recorded in nine healthy subjects during walking and running on a motor‐driven treadmill. Two different types of voluntary modifications of the movement pattern were used: (1) The trunk was kept in an extreme forward or backward tilted position. In both these situations the basic EMG pattern with two periods of activity per stride cycle was maintained during walking, whereas a major shift relative to the stride cycle (25 % of the stride cycle duration) occurred in running with the trunk tilted backwards. The synchrony of the back muscle activation at both sides increased when locomotion was performed with the trunk tilted forwards. The relative duration of the EMG bursts was similar to normal locomotion and corresponded to 15–26% of the stride cycle duration in walking and 23–37% in running. (2) In the other type of modification the subjects were instructed to exaggerate the angular trunk movements either in the sagittal or in the frontal plane. The basic EMG pattern and phase relationships remained in most cases unchanged. One exception was running with exaggerated lateral movements, in which only one period of back muscle activity per stride cycle was observed. The relative duration of the bursts was longer in trials with exaggerated trunk movements as compared to normal locomotion. In walking and running with the trunk tilted forwards or backwards the lumbar back muscles were not always involved as prime movers of the trunk. This was in contrast to the more dynamic situations, in which the back muscle activity appeared to be directly involved in braking and reversing the exaggerated trunk move

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08416.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Eleven human subjects were studied during steady state, controlled mild hypercapnia with resistive loading of either inspiration (R1) or expiration (RE). Minute ventilation and frequency were significantly reduced byR1(P‐<0.01) and even more so byRE(P=<0.001). Tidal volume was unchanged. BothR1andREreduced mean flow in the loaded phase ‐ an effect relatively greater withRE. NeitherRtnorREaltered mean flow in the unloaded phase. Although mean inspiratory flow was unchanged withRE, mouth occlusion pressure (P0.1) was increased (P=<0.01). Functional residual capacity (seven subjects) was increased withRE, but not withR1(P=<0.05). Five additional subjects were similarly studied with and withoutREin whom transdiaphragmatic pressure (PDI) and peak diaphragmatic EMG (EMGDI) were examined. Changes in ventilation, breathing pattern andP0.1were similar to those described above. NeitherPDInor EMGDIwere significantly altered byRE, but withRE, diaphragmatic EMG activity began 50–190 ms before inspiratory flow. In conclusion, ventilation is reduced more byREthan byR1due to greater respiratory phase time. Moderately heavyREdoes not augment inspiratory drive as reflected by mean flow,PDIor EMGDI. WithREand increased FRC,P0.1does not accurately reflect inspiratory drive because of dissociation between EMG and

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08417.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY