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J W Strandhoy

Publications and source records attributed to J W Strandhoy.

49 records · Page 3Linked to original sources
PubMed1973

Effect of volume expansion on sodium excretion in the presence and absence of increased delivery from superficial proximal tubules.

The role of the proximal tubule in the natriuresis after volume expansion was investigated by evaluating sodium excretion both in the presence and absence of increased delivery from the proximal tubule. Proximal delivery was calculated from fractional reabsorption in superficial proximal tubules determined by micropuncture and glomerular filtration rate of the micropunctured kidney. Infusion of Ringer's solution in six dogs increased delivery from the proximal tubule 4.7+/-1 ml/min (P < 0.01) and increased fractional sodium excretion 3.6+/-1.1% (P < 0.025). Infusion of hyperoncotic albumin into the renal artery during sustained volume expansion decreased delivery from the proximal tubule 6.5+/-0.9 ml/min (P < 0.01). Although proximal delivery was restored to below control levels, fractional sodium excretion was significantly increased 2.5+/-0.5% (P < 0.01) as compared with the hydropenic control period. Fractional phosphate excretion was increased 15.5+/-3.7% (P < 0.01) after Ringer's infusion and was decreased 10.5+/-1.6% (P < 0.005) after intrarenal albumin infusion, suggesting that changes in superficial nephron reabsorption were paralleled by changes in reabsorption in deeper nephrons. Similar results were found in six additional dogs in which other factors known to affect phosphate reabsorption were controlled; however, these studies cannot completely eliminate a role for deep nephrons in the natriuresis after intrarenal albumin infusion. Since 70% of the natriuresis after volume expansion was present without increased delivery from superficial proximal tubules, it is likely that increased delivery from the proximal tubule contributes a relatively minor fraction to the natriuresis of volume expansion.

Albumins↗
PubMedDate not supplied

Sympathetic nervous system mediation of acute cardiovascular actions of gamma 2-melanocyte-stimulating hormone.

Peptides of the pro-opiocortin class produce pronounced cardiovascular and natriuretic actions. We have investigated the acute cardiovascular effects of one of the most potent members of this class, gamma 2-melanocyte stimulating hormone (gamma 2-MSH), in rats. Pressor actions of gamma 2-MSH administered systemically were eliminated by ganglionic blockade with chlorisondamine. Peripheral cholinergic blockade failed to affect either the pressor or cardioaccelerator responses to gamma 2-MSH. Administration of gamma 2-MSH (2.0-10.0 micrograms) produced vasoconstriction primarily in the mesenteric and hindlimb vascular beds, while the renal bed showed little response. Infusions of phenylephrine produced pressor responses similar to those found with gamma 2-MSH, which were accompanied by a decrease in heart rate and vasoconstriction in the mesenteric and renal vascular beds. Hemodynamic changes produced by gamma 2-MSH and phenylephrine were blocked or attenuated by alpha 1-adrenergic receptor blockade with prazosin. Direct injection of gamma 2-MSH into the renal artery produced an acute renal vasoconstriction that was not attenuated by alpha 1-adrenergic or ganglionic blockade. These findings and the results of previous publications are consistent with the hypothesis that gamma 2-MSH may produce a centrally mediated activation of the sympathetic nervous system, have direct vasoconstriction actions on the renal vasculature, and inhibit baroreceptor function to produce an increase in blood pressure without an accompanying bradycardia.

Adrenergic alpha-Antagonists↗
PubMedDate not supplied

Importance of the renal nerves for basal and stimulated renin mRNA levels in fetal and adult ovine kidneys.

OBJECTIVE: To investigate the effect of renal denervation on renin mRNA levels in fetal and nonpregnant adult ovine renocortical tissue and in isolated juxtaglomerular cells under basal conditions and after stimulation. METHODS: The left kidney was denervated and the right kidney subjected to a sham procedure in nine ovine fetuses (136-141 days' gestation) and 20 nonpregnant ewes. After 5-7 days the denervated and intact kidneys were obtained, and renin-containing renal cortical cells were isolated and cultured overnight. Then cells were treated with isoproterenol, forskolin, or isomethylbutyl xanthine (IBMX) for 4 hours. Total RNA was isolated and renin mRNA measured by RNase protection assay. Cyclic adenosine monophosphate (cAMP) levels were measured in the incubation medium with a competitive enzyme immunoassay. RESULTS: In adults, basal renin mRNA levels were significantly lower in denervated than in sham-operated kidneys. No difference was noted between denervated and intact fetal kidneys. Renin mRNA levels were significantly higher in fetal than in adult kidney tissue, and cells from fetuses had greater increases in renin mRNA after stimulation than did cells from adults. Fetal cells also released more cAMP into the incubation medium, and there was a correlation between cAMP and renin mRNA levels. CONCLUSIONS: The data indicate the effects of renal denervation on renin mRNA expression in the kidney are age dependent and that the fetus in late gestation has a mechanism for maintaining renin mRNA levels after denervation, which is absent or nonfunctional in the adult.

1-Methyl-3-isobutylxanthine↗