摘要:

The present study documents the effects of hypophysectomy on the NaCl‐stimulated release and on the basal secretion rates of ANP from rat atriain vitro.Three weeks before the experiments rats were subjected to hypophysectomy or to a corresponding sham operation. Atria were excised and superfused in an organ bath with a physiological buffer solution (PBS, 294 mosmol kg‐1). After a control period of 5 min, superfusion was made with hyperosmotic NaCI (330 mosmol kg‐1) for 10 min, and then again with PBS, but now for 15 min. Atria were paced with field stimulation (4 Hz, 20 V, 1 ms) and the resting tension was kept at 5 mN. The sham‐operated animals responded with a significant increase (P<0.05) in the secretion rate of ANP (from 137 ± 13 pg ml‐1[n = 35] to 235 ± 24 [n = 34], means + SE) to the NaCI stimulus. The hypophysectomy blunted the ANP response to hyperosmotic NaCl. In addition, basal secretion rate was signficantly (P<0.001) lower in the hypophysectomized than in the sham‐operated animals during the whole experiment. Gel filtrations revealed that, during the hyperosmotic NaCI, both groups secreted exclusively ANP 1–28. We conclude that hypophysectomy blunts the basal as well as stimulus‐inducedin‐vitrorelease of

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08695.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The possible involvement of neuropeptide Y (NPY) in sympathetic control of renal blood flow was investigated in the pigin vivo.Exogenous NPY caused renal vasoconstriction with a threshold effect at an arterial plasma concentration of 164 pmol 6‐1. Stimulation of the renal nerves (0.59, 2 and 10 Hz) in control animals evoked rapid and frequency‐dependent reduction in renal blood flow and overflow of NPY‐like immunoreactivity (NPY‐LI) and noradrenaline (NA) from the kidney, suggesting co‐release from sympathetic nerves. Following the administration of the α‐ and β‐adrenoceptor antagonists phenoxybenzamine and propranolol, the vasoconstrictor response to exogenous NA was reduced by 98%, whereas that of NPY was unaltered. The response to nerve stimulation with 0.59 Hz was abolished, whereas relatively slowly developing reductions in renal blood flow by 7 and 28%were obtained upon stimulation with 2 and 10 Hz respectively. The nerve stimulation‐evoked overflow of NA at 0.59 and 2 Hz, but not at 10 Hz and not that of NPY‐LI, was enhanced after adrenoceptor blockade. Twenty‐four hours after reserpine treatment (1 mg kg‐1i.v.) the contents of NPY‐LI and NA in the renal cortex were reduced by 80 and 98% respectively. Sectioning of the renal nerves largely prevented the reserpine‐induced depletion of NPY‐LI, but not that of NA. Nerve stimulation of the denervated kidney with 2 and 10 Hz 24 h after reserpine treatment evoked slowly developing and long‐lasting reductions in renal blood flow by 6 and 52% respectively. These responses were associated with overflow of NPY‐LI, which was similar to and threefold higher than that observed in controls at 2 and 10 Hz respectively, while no detectable overflow of NA occurred. Repeated stimulation with 10 Hz resulted in a progressive fatigue of the vasoconstrictor response and the associated overflow of NPY‐LI, giving a high correlation (r = 0.86, P<0.001) between the two parameters. It is concluded that NPY is a potent constrictor of the renal vascular bed. Furthermore, although NA is the likely transmitter mediating most of the responses to low to moderate nerve activation under control conditions, the data suggest that NPY may mediate the non‐adrenergic reductions in renal blood flow evoked by high‐frequency sympathetic nerv

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08696.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

We compared the effects of electrical stimulation of the splanchnic nerves and infusions of neuropeptide Y, noradrenaline or a combination of the two on pancreatic vascular resistance and exocrine and endocrine secretion. For these studies we used isolated perfused pig pancreas with preserved splanchnic nerve supply. The exocrine secretion was stimulated with physiological concentrations of secretin and cholecystokinin octapeptide. Noradrenaline and NPY at 10‐8M both increased pancreatic perfusion pressure. Their effects were additive and similar in magnitude to that of electrical stimulation of the splanchnic nerves at 4–8 Hz. Nerve stimulation as well as NPY and noradrenaline infusions inhibited exocrine secretion, but an additive effect could not be demonstrated. Neither NPY nor noradrenaline could reproduce the stimulatory effect of nerve stimulation on glucagon secretion, nor the weak inhibitory effect on somatostatin secretion. NPY alone had no effect on insulin secretion and did not influence the inhibitory effect of noradrenaline. It is concluded that NPY is likely to cooperate with noradrenaline in the control of pancreatic blood flow, whereas its role in the control of pancreatic secretion is likely to be of minor importance, if

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08697.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

During the early neonatal period of rapid growth in the mouse, increased plasma levels of erythropoiesis stimulating factor(s) (ESF) have been found when measured by anin‐vitrobioassay technique. It is unclear whether these increased ESF levels represent increased levels of circulating erythropoietin (Ep) alone or Ep in combination with other less‐defined erythropoietic stimulatory factors. To examine this issue, plasma from neonatal mice of varying post‐natal ages and from normoxic and hypoxic adult mice was studied. We found that plasma Ep levels measured by radioimmunoassay (RIA) correlated significantly within‐vitrobioassayed ESF levels (r = 0.84, P<0.0001, n = 21). Although anin‐vivobioassay for plasma Ep proved too insensitive for rigorous correlation with data from the RIA andin‐vitrobioassay, thein‐vivodata were in qualitative agreement with the other two, more sensitive, assays. In all three assays the highest plasma levels were observed in the 20‐day‐old mice and in adult mice which had been subjected to hypobaric hypoxia for 8 h. Based on the strong agreement of the results obtained with the RIA and thein‐vitrobioassay in both neonatal and adult mouse plasma, we conclude that the high plasma ESF levels of 20‐day‐old mice measured with thein‐vitrobioassay are largely immunochemically identifiable Ep. However, the data also suggest the presence of non‐Ep factors in neonatal plasma which st

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08698.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

1 Transport pathways for Na+and Br‐across noradrenaline‐stimulated frog skin, in which the sodium channels in the apical membrane had been blocked with amiloride, were examined by pre‐steady‐state flux ratio experiments.2 To analyse the experiments, equations are derived from which the fluxes through two parallel pathways can be determined if these differ with respect to the flux ratio as well as the mean passage time for the ion in question.3 The fluxes of Na+and Cl‐were followed over a period of 3 h and it was found that about 1 h after addition of noradrenaline time‐invariant fluxes could be achieved. In that period inward and outward tracer fluxes of Na+and Br‐(used as a substitute for Cl‐) were followed during the build‐up of isotope in the tissue until steady‐state fluxes were attained.4 The experiments showed that when the Na channels of the capital cells are blocked the glands provide the major pathway for sodium transport across the skin. The efflux of Br‐can be separated into two components. A fast one through the mitochondria‐rich cells, which is the pathway for passive anion fluxes, and a slower one through the glands. No influx through the slow transport pathway could be detected. In some skins exchange of Br‐through the mitochondria‐rich cells is revealed. An anion exchange mechanism also appears to be present in the baso

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08699.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Serosal amiloride inhibits Na+, K+and Cl‐efflux and reduces short‐circuit current and transepithelial conductance in noradrenaline‐stimulated frog skin in which the sodium channels in the apical membrane are blocked by amiloride. BIG (benzimidazoleguanidine) inhibits Na+and K+efflux and reduces the short‐circuit current. In some skins BIG decreased and in others it increased Cl‐efflux and conductance. The variable response appears to be due not only to inhibition of salt extrusion from the gland cells but also to activation of Cl‐transport through the mitochondria‐rich cells, since it was shown that BIG could increase Cl‐efflux in gland‐free preparations. Different target mechanisms in the gland cells where the two substances may exert their eff

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08700.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The temporal changes in muscular blood flow and in the release of ions and metabolites have been studied during and after short‐lasting isometric contractionsBlood velocities in the human femoral artery were measured using pulsed bidirectional Doppler ultrasound equipment during single contractions of the quadriceps muscle group. Contractions of 5 s and 30 s duration and at a tension of 10% MVC (maximal voluntary contraction) were investigated. Even the contractions of 5 s duration caused conspicuous post‐contraction increases in femoral arterial flow..The following substances were analysed in the femoral vein during and following the contractions: potassium, lactate, inorganic phosphate, calcium, sodium, oxygen and haemoglobin. Following contractions of 5 s duration, an increase in the venous potassium concentration (by 0.9mM) was found, but there was no change in concentration of any of the other substances analysed. Following contractions of 30 s duration a more marked increase in the venous potassium concentration (by 1.5 mM) was found, and in addition substantial changes in venous lactate concentration and oxygen saturation. There were small but statistically significant changes in the concentrations of inorganic phosphate and calcium, but no change in the sodium concentration.The time‐course and magnitude of the changes in venous potassium concentration fit well with the idea that potassium is important in the initiation and regulation of the functional hyperaemia in contracting mu

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08701.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

To determine the variability in fibre areas in the human vastus lateralis muscle, cross‐sections (15 μm) of whole autopsied muscles from eight young men have been prepared, and the cross‐sectional area (CSA) of 375 type 1 and 375 type 2 fibres has been measured in five different regions throughout each muscle. The CSA of both fibre types varied significantly within all muscle cross‐sections. Fibres in the deep parts of the muscle were larger than superficially. There was a significant correlation between the CSA of the two fibre types within each region: if a fibre of a given type was small, or large, the other fibre type was also small, or large. The CSA of type 2 fibres was larger than the CSA of type 1 fibres in 26 of the 40 regions: regions with type 1 fibres larger than type 2 fibres were mostly (71%) found deep in the muscle. The standard deviation of the CSA of type 1 fibres was significantly larger than for type 2 fibres in 35 of the 40 regions. In conclusion, the CSA of the different fibre types in the vastus lateralis of young men varies non‐randomly. The pattern of variation, both throughout the muscle and in small sample regions, supports the general opinion that the functional demands placed on the fibre population are an important factor in the development of the fibre pr

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08702.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

In order to study the regulation of β‐adrenergic receptor number and function in response to prolonged physical effort, lymphocytic β‐adrenoceptor density (determined by (‐)[125I]iodocyanopindolol binding), lymphocytic basal and isoproterenol‐stimulated cyclic AMP (cAMP) production and concentrations of plasma catecholamines were measured before and during 3 h running exercise in eight healthy volunteers. A significant (P<0.01) increase of the lymphocytic β‐adrenoceptor density from 45±4 to 81 ± 9 fmol mg‐1protein (mean ± SEM) took place during the first hour of exercise. As the exercise was continued for up to 2.1–3 h, the receptor densities did not change significantly any more and remained elevated (72 ± 9 fmol mg‐1protein) in comparison to the resting levels (P<0.02). The isoproterenol‐stimulated cAMP production of the lymphocytes increased during the first hour of running from 190 ± 36 to 269 ± 56 pmol mg‐1protein (P<0.01) and returned to the resting level at the end of the exercise (182 ± 38 pmol mg‐1protein). The mean levels of plasma catecholamines increased ˜ sixfold during the first hour of exercise and remained elevated until the end of the running. This study demonstrates that the β‐adrenergic receptor system is activated in lymphocytes during prolonged aerobic physical exercise. This activated state becomes, however, attenuated within 2–3 h of exercise as indicated by a diminishing ability of β‐adrenoceptors to media

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08703.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

In the present study the possible influence of capsaicin on human arterial coronary tonein vitrowas studied in relation to the vasodilatory properties of calcitonin gene‐related peptide (CGRP), substance P (SP) or neurokinin A (NKA). In addition, the influence of vasoactive intestinal polypeptide (VIP) and somatostatin (SOM) on the arteries was investigated.CGRP application to potassium‐pre‐contracted human epicardial coronary arteries (0.4–0.6 mm in inner diameter) induced a concentration‐dependent, long‐lasting relaxation. SP also relaxed these pre‐contracted arteries, but the relaxation was transient and tachyphylaxis developed rapidly upon repeated administration. SP tachyphylaxis did not influence the relaxatory effects of CGRP. Furthermore, pre‐incubation with gossypol, an inhibitor of the formation and release of endothelium‐derived relaxing factors (EDRF), completely abolished the effects of SP without influencing the dilatory action of CGRP. NKA only induced a very minor relaxation of the pre‐contracted arteries. Both VIP and SOM concentration‐dependently relaxed the pre‐contracted arteries.Capsaicin evoked a relaxation of the potassium‐pre‐contracted arteries. This effect was not influenced by SP tachyphylaxis or gossypol incubation. Thus, CGRP but not SP mimics the vasodilatory effects of capsaicin on human coronary arteries. This suggests that CGRP rather than SP is likely to mediate the relaxatory effects seen upon activatio

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08704.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY