Sidney Solomon

Inherited Renal Cysts in Rats

A strain of rats that form renal cysts has been developed. The number of visible cysts increases with age after animals are 20 days old. Micropuncture studies indicate that the cystic fluid has a variable sodium concentration, but that the ratios of inulin concentration in tubular fluid to that in plasma are high.

In vitro Evidence for a Renotrophic Factor in Renal Compensatory Hypertrophy

A plasma factor has been hypothesized to initiate compensatory growth of the remaining kidney following unilateral nephrectomy. Evidence supporting the existence of this factor has been obtained in studies of hamster renal cortical cells grown in monolayer tissue culture. These cultured cells resemble renal epithelium in electron micrographs. The incorporation of 3H-uridine into RNA was significantly increased in those cultures incubated in plasma from uninephrectomized hamsters (UP) above those containing sham plasma (SP) at 10 and 15 % plasma in the medium. The uptake of uridine into the cy toplasmic fraction of those cultures incubated for 4, 6, 8, 10 and 24 h and in the nuclear fraction for 2, 4, 6, 8 and 24 h in UP was significantly greater than those incubated in SP. Plasma from partially hepatectomized hamsters did not increase the growth rate of this tissue culture over those cultures incubated in SP. Dialysis of UP does not affect its growth characteristics. Therefore, a renotrophic factor is present in the plasma of uninephrectomized hamsters which increases the uptake of uridine into renal tissue cultures.

Sodium and Chloride Movement into the Central Canal of Cat Spinal Cord.

Summary Net fluxes of sodium, chloride and water across the ependymal lining of tral canal and that a sodium transport system is involved in this process. We are indebted to Dr. Leonard Napolitano of the Department of Anatomy for his help with the micrographs.

Action of alkali metals on papillary-cortical sodium gradient of dog kidney.

Summary Anesthetized dogs were infused with isotonic solutions of LiCl, RbCl or CsCl and the cortico-papillary ion gradients of the kidneys were studied by tissue analysis. Lithium content increases from cortex to papilla. Tissue content for rubidium and caesium decreases from cortex to papilla. None of the alkali metals changed the relationship between papillary urinary sodium content and urine osmolality.

Absolute Rates of Sodium and Potassium Reabsorption by Proximal Tubule of Immature Rats

Using micropuncture procedures, the rate of proximal tubular sodium and potassium transport in mannitol-infused rats has been studied. Tubular diameter and length increase with animal size, but the rates of change are greater in small animals than in larger animals. SNGFR increases with body weight in a linear fashion. Animals from reduced litters have larger SNGFR than do animals from intact litters and males have higher SNGFR than do females. Absolute transport rates for sodium and potassium increase with age and parallel the increases in SNGFR. These results indicate that the predominant factor maintaining proximal glomerular tubular balance as animals grow is an increase in absolute proximal transport rates. With a 50-fold change in SNGFR, change in transport rate accounts for about a 10-fold change, and the rest of the increase in overall proximal absorption is accounted for by an increase in surface area.

Evidence that the Renal Response to Volume Expansion Involves a Blood-Borne Factor

The effect of blood volume expansion in immature rats by blood from infants (J to J expansion) and mature animals (A to J) has been studied. A to J expansion results in an increased renal response to expansion which is greater than J to J, but not as great as when mature animals are expanded with blood from other matures (A to A) or pooled blood from infants (J to A). A to A and J to A expansions show no significant differences in renal responsiveness. The lack of an immature response is not due to differences in animal hydration since 2.5% volume expansion is on the flat part of dose response curve. Part of the scatter of the adult response is related to absolute levels of GFR which might indicate the existence of a filterable natriuretic factor or, alternatively, a dependence of renal responsiveness on filtered load. These results are interpreted to indicate that mature rats contain a natriuretic factor or an inhibitor of an antinatriuretic factor which is blood borne and is probably secreted in blood volume expanded rats.

Renal Response to Ringer Expansion in Developing Rats

Male rats were studied between 20 and 60 days of age. Standard renal clearance techniques were used. The efficiency of the diuretic response, the sodium response, and the potassium response were calculated as defined previously. Results indicate that both diuretic and sodium efficiency is lower between the ages of 20 and 30 days as compared to 40 and 60 days of age, whereas potassium efficiency shows no age dependence. In morphological studies, it has been observed that the proximal tubule cells of 22-day-old rats show changes in lateral intercellular spaces with comparable features to those of mature animals. The spaces widened during volume expansion. The change is quantitatively the same as that found in mature rats. Both blood pressure and hematocrit show continuous increase with age. The response of Ringer infusion in both immature and mature animals may be a mixed response involving changes in physical factors and renal responses to volume expansion per se.

Prolactin-Induced Stimulation of Rat Renal Adenylate Cyclase and Autoradiographic Localization to the Distal Nephron

Prolactin was shown to activate adenylate cyclase in broken cellular enzyme preparations from rat renal medulla. Likewise, vasopresin was effective on this enzyme system. Parathyroid hormone was similarly active in the renal cortex. The simultaneous administration of vasopressin and prolactin to medullary kidney slices did not result in an additive effect in stimulating medullary adenyl cyclase. Audioradiographic techniques revealed a selective and prolonged localization of intravenously injected 125I-prolactin to the thick limb of the loop of Henle, the distal tubule and the collecting duct. It is concluded that prolactin activates medullary adenylate cyclase, and may do so by occupying ADH receptors.

Postnatal changes of water and electrolytes of rat tissues.

Summary Electrolyte and water contents of heart, liver, kidney, spleen, ovaries, and testes were analyzed in rats between 2 and 100 days of age. Tissues were dried to constant weight to measure water content. Electrolyte content was determined using emission spectrophotometry. At all times, the liver contained the least amount of water; the kidney, spleen, and heart had an intermediate water content which were approximately equal to each other; the testes and ovaries contained the highest content of water. Water contents of the liver, heart, spleen, and kidney fall from 2 to 23 days of age and then remain constant at adult levels. The water contents of testes and ovaries remain relatively constant throughout the period studied. Tissue Na content of the heart, liver, kidney, spleen, and testes is high relative to K in the early postnatal period and decreases with age, reaching a minimum at 37-44 days of age. The most unexpected result of this study is the finding that the Na content of the ovary parallels that of the kidney papilla during all the periods examined. In both these tissues, Na content is low at 16 days of age and is higher thereafter. These results demonstrate a dissociation between maturation of water and electrolyte balance. This work was supported by two grants from the National Science Foundation, BMS-72-02344-A02 (to S.S.) and PCM-71-01528 (to A.R.). We also wish to thank Ms. Carolyn Sanborn and Ms. Susan Hathaway for their expert technical assistance.

Aldosterone and growth hormone: influence of diet and hypophysectomy on rat renal response.

Summary Experiments in hypophysectomized rats indicated that though growth hormone and aldosterone could produce summative antinatriuresis when given together, neither growth hormone nor the hypophysis appeared necessary for aldosterone to exert a profoundly antinatriuretic effect. Previous dietary history, however, may modify the response of the hypophysectomized rat to aldosterone. In sodium-replete rats, the response was antinatriuretic and antidiuretic, while in sodium-depleted rats, the response was diuretic and did not significantly modify sodium excretion. Special thanks are rendered to Dr. I. S. Edelman who suggested some of the experiments herein reported. The excellent technical assistance of Mrs. Lucy Moore is appreciated.