Hemorrhage in normal man: effect on renin, cortisol, aldosterone, and urine composition

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A micromethod for measurement of renin in the plasma and kidney of rats

A new micromethod for the measurement of renin activity and substrate in 0.1 ml of rat plasma and in 1 mg of rat renal tissue is described. In the procedure a rat substrate free of renin prepared from previously nephrectomized animals is used. Incubation is carried out in the presence of Dowex resin 50W-X2 (NH4+) for 12 hours, at pH 6.5, with an excess of rat substrate. Angiotensin formed during incubation is measured by a pressor assay in the rat. The reproducibility of the procedure was excellent. Recovery of angiotensin in amounts from 10 to 500 mμg was 77%. This method permits repeated measurements of renin activity in rats during acute experiments and in any physiological procedure. It can readily be adapted to other species.

Renal angiotensinase activity. Its localization and the effects of mercury

A rat bioassay technique was employed to determine the localization and properties of the angiotensinase activity present in kidney homogenates of anesthetized rats. The angiotensinase activity per gram of renal cortex was four times greater than renal papilla or medulla. The complete destruction of proximal renal tubular cells by mercuric chloride resulted in losses of cortical angiotensinase activity averaging 40% of control values. The destruction of cells of both the proximal and distal renal tubules by sodium potassium tartrate caused a 90% reduction in angiotensinase activity. Marked reductions in cortical angiotensinase activity were measured in rats injected with meralluride 2 hours previously. The addition of meralluride to in vitro systems of normal rat kidney homogenates caused similar depressions of angiotensinase activity. The presence of reduced glutathione in the reaction media interfered with the ability of meralluride to inhibit angiotensinase and enhanced the activity of this enzyme to greater than normal levels in the absence of the mercurial. Ammonium ion in a concentration of.18 m inhibited angiotensinase activity of renal cortical homogenates by a moderate degree. When both meralluride and ammonium were present in the homogenate system their effects to depress angiotensinase appeared additive.

Effect of hemorrhage on arterial plasma renin activity in the rabbit

Arterial plasma renin activity in the rabbit was measured at the beginning and end of a brisk hemorrhage and 40 min later. Activity rose to a mean of two and one-half times the control value during the hemorrhage, and was five times greater than the control 40 min later. The rise in plasma renin activity was not due to anesthesia, as light pentobarbitone produced no change. Conscious rabbits, severely bled from a carotid cannula, 2 to 5 hr after an ether anesthetic, also showed an increase in plasma renin activity at the end of hemorrhage. Forty-eight hours after both kidneys had been removed, renin activity was virtually absent and did not rise after hemorrhage.

The passage of drugs across the rat intestine in vitro

The in vitro methods of Smyth & Taylor (1957) and everted sac technique of Crane & Wilson (1958) have been evaluated for studying the passage of ferrioxamine-B hydrochloride and its derivatives, glutethimide, thalidomide, a polypeptide, salicylic acid, aniline and phenol red from the mucosal to serosal side of the rat intestinal barrier in vitro. The ferrioxamines were not significantly absorbed, glutethimide was more rapidly absorbed than thalidomide, the polypeptide was broken down rapidly and appeared as amino-acids in the serosal fluid, salicylic acid and aniline were found in the serosal fluid but phenol red was little absorbed. Although allowance must be made for differences in the transit pathways of in vivo and in vitro systems because of the non-functional nature of the capillary network in in vitro studies, our results suggest that these methods can supply useful information on the permeability characteristics of newly developed drugs through the intestinal barrier.

Measurement of renin activity in human plasma

A method is described for estimating plasma renin activity by using renin substrate present in plasma. This method differs from other indirect renin assay methods by (1) incubation in the absence of ions thus establishing conditions for zero order kinetics for the reaction between endogeneous renin and substrate and (2) the use of angiotensinase inhibitors di-sodium ethylenediamine tetraacetic acid ( EDTA ) and d-isopropylfluorophosphate (DFP). Recoveries of renin added to plasma in levels similar to those occurring in plasma are 85% SD ±7%.

The incubation was done at pH 5.5 which was shown to be the optimum for human renin reacting with human substrate.

By incubating human plasma samples with known quantities of human renin, evidence was obtained suggesting that factors other than enzyme or total substrate concentrations affect the velocity of angiotensin formation. This variability of reaction rate may be explained by the existence of an inhibitor or activator in this system or by a variation in the type of substrate.