摘要:

The study was performed in order to determine the effect of venous pressure elevation induced by unilateral partial renal venous ligation upon total renal blood flow and filtration fraction in the dog kidney. An anaesthesia with no known inhibitory effect on sympathetically mediated vasoconstriction was used. During control conditions instantaneous increase in renal venous pressure to 60 mmHg induced a decrease in renal blood flow (66 ±4%) corresponding to an ipsilateral vasoconstriction which was completely abolished following (1) surgical denervation of the kidney, (2) local a‐receptor blockade of the kidney, and (3) application of lidocain on the kidney surface. The most striking feature during step increase in renal venous pressure to 40 mmHg was an increase in renal vascular conductance. Renal venous pressure elevation of more than 40 mmHg induced a vasoconstriction, but the vasoconstrictor response was less pronounced as compared with that observed during instantaneous increase in renal venous pressure to the same level. The results strongly suggest that venous stasis of more than 40 mmHg activates an adrenergic sympathetic vasoconstrictor reflex comprising the spinal cord. The reflex is probably elicited from stretch receptors located in the renal capsule. Changes in filtration fraction at venous stasis during the experimental conditions indicate that renal venous pressure elevation activates mechanisms other than neural ones accounting for the reduction in the filtration fracti

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07554.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07622.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Potassium secretion may depend on the transport rate of Na, K‐ATPase in basolateral cell membranes of distal tubular cells. To examine this hypothesis experiments were performed in anaesthetized dogs during inhibition of proximal potassium reabsorption by acetazolamide or mannitol (fractional potassium excretion 1.2‐1.4) or additional stimulation of potassium secretion by ethacrynic acid (fractional potassium excretion 2.1). Ouabain in a dose which inhibits 70–80% of the Na, K‐ATPase activity reduced fractional potassium excretion to 0.8‐0.9 by an effect on distal tubular secretion since potassium transport in the proximal tubules was not affected. Ouabain‐sensitive potassium excretion varied in proportion to ouabain‐sensitive sodium reabsorption during variation in glomerular nitration rate, even at urinary sodium concentrations exceeding 80 mmol 1‐1. In experiments without ouabain, saline infusion raised potassium excretion and sodium reabsorption until maximal Na, K‐ATPase transport rate was reached, as judged from heat production measurements, but not during further increments in urine flow. After inhibition of Na, K‐ATPase activity by hypokalaemia, potassium excretion and cortical heat production remained constant over a wide range of urine flow and sodium excretion. We conclude that potassium secretion is dependent on intact Na, K‐ATPase activity and is stimulated by sodium delivery to the distal nephron until maximal transport rate of

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07555.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07623.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The soluble proteins (chromogranins) of bovine chromaffin granules have been studied by micro‐osmometry with semi‐permeable membranes (UM2, PM10 and PM30 with cut‐offs>1,>10 and>30 kD, respectively) at I =0.15 and pH 5–8 for protein concentrations up to 20 mg ml‐1. After lysis of chromaffin granules in phosphate buffer pH 6, the released chromogranins behaved as aggregating solutes, consistent with an inconspicuous osmotic pressure contribution from the chromogranins at the protein concentration of the intact granules. Thus, in the presence of phosphate about 90% of the molecules behaved as colloids withMr=30,300 atc =o. After lysis in phosphate‐free buffers the chromogranins behaved as highly non‐ideal solutes in a manner which was incompatible with isotonicity at the protein concentration of the intact granules. About two‐thirds of the molecules in the lysates in Na‐succinate pH 5–6 and K‐acetate pH 6 exhibitedMr= 66,000 and 79,000, respectively. In dilute solutions (<12mg protein ml‐1) and ATP/protein ratios corresponding to those in the intact granules, the UM2 pressures were markedly increased, indicating release of polypeptides withMr2000–3000 from aggregates. CaCl2was without specific effect on the colloid osmotic pressures but reduced the ATP‐dependent increase in pressure, suggesting release of molecules twice the size of those released by ATP alone. A model is presented for the contribution of the chromogranins to osmotic pressure regulation in the bovine adrenomedullary cat

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07556.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The effect of direct intrathecal injection ofp‐chloroamphetamine (PCA) into the lumbar subarachnoid space was investigated in mice. PCA (0.6–20 μg) induced a dose‐related prolongation of response latencies in the tail‐flick test, but failed to affect the hind‐paw lick response in a hot‐plate test employing slowly rising temperature. PCA (5μg)given intracerebroventricularly did, however, significantly elevate the response temperature in the hot‐plate test. The antinociceptive effect of PCA in the tail‐flick test was prevented by spinalization, by pretreatment with the selective serotonergic re‐uptake blocker zimelidine (20 mgkg‐1i. p.) and by the serotonin synthesis inhibitorp‐chlorophenyl‐alanine (300 + 300+ 150 mgkg‐1i. p. 72, 48 and 24 h before test). It is concluded that PCA given intrathecally releases serotonin from spinal terminals, which may under certain condit

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07557.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The influence of muscle contraction, induced by electrical stimulation, on the activity of glycogen phosphorylase, the contents of high‐energy phosphates, hexosemonophosphates and lactate have been studied in isolated extensor digitorum longus (EDL) and soleus muscles from rats. The activity of phosphorylasea + bwas about nine times higher in fast twitch muscles (EDL) than in slow‐twitch soleus and remained unchanged during the stimulation. A pronounced increase of phosphorylaseaoccurred during the stimulation in EDL muscle. Stimulation with a frequency of 50 Hz for 10 s and 2 Hz for 90 s resulted in a 44‐fold and five‐fold increase in phosphorylasea, respectively. In contrast, stimulation of soleus muscle resulted in only a minor increase of phosphorylasea. The rate of glycogenosis increased in both muscles during the stimulation but the increase was four to five times higher in the EDL than in soleus muscle. The content of phosphocreatine (PCr) before stimulation was much higher in EDL than in soleus but similar after the stimulation. This resulted in a three‐ to four‐fold higher release of inorganic phosphate (P1) in EDL than in soleus during contraction. Pi has previously been shown to be present in a limiting amount for the activity of phosphorylase and the increase during contraction is of importance for increasing the glycogenolytic rate. It is concluded that the higher glycogenolytic capacity in fast‐twitch muscles compared to slow‐twitch muscles is due to: (1) higher content of phosphorylase a + b, (2) higher degree of transformation of the enzyme into the a form during contraction, and (3) higher content of PCr, which liberates a large amount of P1dur

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07558.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The proposed calcium promotor BAY K 8644 contracted feline basilar arteries partially depolarized by iommol‐1‐1potassium in a concentration‐dependent manner (EC50value: (2.1 ± 1.2) × 10‐9mol l‐1). The concentration‐response curve for prostaglandin (PG) F2αwas displaced to the left after pretreatment with BAY K 8644. PGF2αinduced a biphasic contraction in calcium‐free medium as has been described previously. The second PGF2α‐induced contraction phase in calcium‐free medium was abolished by pretreatment with nifedipine or diltiazem. BAY K 8644 restored the second phase in arteries pretreated with nifedipine, but not in vessels pretreated with diltiazem. The findings suggest that BAY K 8644 acts as a promotor of calcium‐influx, probably by interaction with the ‘dihydropyridine receptor’ in the cell membrane, and also provide support for the view that PGF2αre

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07559.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The regulation of glycogenolysis in human muscle during isometric contraction without and with adrenalin infusion has been investigated. The content of cAMP in muscle increased three‐fold during the infusion. Total glycogen phosphorylase and synthetase activities were unchanged during contraction without and with adrenalin infusion. The fraction of phosphorylase in theaform was in resting muscle 26% and at the end of contraction 24%. During adrenalin infusion phosphorylaseaincreased to 80%. Contraction during continued infusion resulted in a decrease of phsophorylaseato 42%, despite persistently increased cAMP content in muscle. The activity of synthetase I decreased to about half of the initial value during adrenalin infusion and contraction both without and with the infusion. The rate of glycogenolysis in muscle during contraction was not significantly changed by the infusion. Phosphocreatine (PCr) decreased during the contraction and the decrease was similar without and with adrenalin infusion. The amount of inorganic phosphate (P1) accumulated in muscle during contraction was lower when adrenalin was given due to a greater accumulation of hexosemonophosphates. It is concluded that the rate of glycogenolysis in muscle during contraction without and with adrenalin infusion is a function both of phosphorylase in the formaform and the availability of Pj at the active site of the enzym

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07560.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Islets isolated fromob/obmice which had been fed a vitamin D‐deficient diet released significantly less insulin in response to glucose than did vitamin D‐replete islets but showed normal net45Ca2+uptake. To determine whether vitamin D3has a direct effect on the pancreatic B cell, islets fromob/obmice on a normal diet were exposed to vitamin D,in vitrofor 1 week or only 3 h, and then glucose‐stimulated45Ca2+uptake and insulin release were measured. Exposure to 1 nM or 1 μM vitamin D3for 1 week stimulated45Ca2+uptake in the presence of 3 mti, but not 20 mM glucose, and did not affect insulin release. Exposure to vitamin D3for 3 h did not significantly increase net45Ca2+uptake although there was a tendency to such an effect (P= 0.10). In conclusion, vitamin D‐deficiencyin vivosuppressed subsequent glucose‐stimulated insulin releasein vitroand this effect may be due to a direct effect of the sterol (or one of its metabolites) on calcium handling by

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07561.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY