Paul A. Rondell

Protracted Pressor Response to Angiotensin After Bilateral Nephrectomy in Rats

The pressor response of nephrectomized rats to an injection of renin is marked by a prolonged stable plateau. A similar, prolonged response to angiotensin has been demonstrated and the following aspects of this pressor effect were evaluated. 1. The protracted response was shown not to be due to a persistence of angiotensin in the blood of nephrectomized animals. There are several indications from unrelated studies that angiotensin is destroyed rapidly. Cross-circulation experiments indicate that during the protracted pressor phase blood levels of constrictor materials have fallen to undetectably low levels. 2. No evidence could be obtained to indicate that the neurogenic buffer system is involved in the development of the protracted response. Ganglionic blockade was ineffective in preventing its development. 3. The hemodynamic basis for the response must be a persistent increase in total peripheral resistance (TPR) since there is no increase in cardiac output (CO) in response to the angiotensin infusion. Before infusion, the CO of nephrectomized animals is higher than that of sham-operated control animals. 4. The increase in TPR must be due to an increase in geometric hindrance for no changes in hematocrit or in viscosity result from angiotensin infusion. Blood viscosity is lower in nephrectomized than in sham-operated animals, but this can account for only part of the lower pre-injection control pressure seen in this group. It appears that in animals depleted of endogenous renin, a large infusion of angiotensin increases vascular resistance by some non-neurogenic, non-humoral mechanism which may represent another type of vascular tone.

Evidence for Humoral Factors in Renoprival Hypertension

Plasma of renoprival hypertensive rats was found to have an exaggerated constrictor effect on isolated rat aorta strips, however, no pressor effect was produced in acutely nephrectomized rats cross-circulated with renoprival hypertensive animals. It is suggested that if the constrictor element of the plasma from renoprival hypertensive rats is not just an artifact of the aorta strip assay technic but does exist and play a role in renoprival hypertension, it does so by acting on arterioles sensitized by the chronic a-renal condition.

Immunoprecipitation of diffusing antigens from single agar gel-suspended erythrocytes (cytoimmunodiffusion).

Summary When agar gel-suspended erythrocytes are exposed to a specific antibody and then lysed, the intracellular soluble antigen diffuses in all directions and reacts with the surrounding antibody. This reaction produces a characteristic granular precipitate around individual cells which, upon proper fixation, can be studied by light or electron microscopy.

FOLLICULAR FLUID ELECTROLYTES IN OVULATION.

Conclusions The Na and K concentration of follicular fluid is similar to that of plasma. The K concentrations of diestrus, estrus, and pre-ovulatory rabbit follicles are not measurably different. Average [K] values are slightly above those for normal plasma. Na concentration of diestrous follicles was somewhat higher than that of plasma, whereas the Na content of fluid from estrous and pre-ovulatory follicles was somewhat lower.

STRAIN DIFFERENCES IN RESPONSE TO WHOLE BODY IRRADIATION AND SHIELDING PROCEDURES IN THE RAT

Over the past 3 years we have used 421 rats in studies of the protective effect of lead shields against iradiation death. Two strains of rats were used throughout these studies. The strain that was more sensitive to whole-body irradiation was also the one more effectively protected by the shielding procedure. Previous work indicated that shielded tissues made some contribution to the irradiated animal which enhances its chances of survival. From the current study it is concluded that the strain in which the tissues are best able to make this type of contribution is also the one in which this contribution is most readily destroyed by irradiation. (auth)