Analysis of the pinocytic process in rat kidney. I. Isolation of pinocytic vesicles from rat kidney cortex

Pinocytosis was induced in rat kidney by exposure to horseradish peroxidase (HRP). Pinocytic vesicle preparations were enriched after homogenization of kidney cortex by differential centrifugation and free-flow electrophoresis with HRP as an exogenous marker. Vesicles were identified by enzymatic analysis and by electron microscopy, including specific staining procedures. Typical brush-border enzymes such as alkaline phosphatase, aminopeptidase, 5'-nucleotidase, lysosomal acid phosphatase, and mitochondrial succinic dehydrogenase were reduced in the vesicular fraction, compared to the kidney cortex homogenate. Glucose-6-phosphatase and Na(+)-K(+)-ATPase were only slightly increased in the fraction. These results indicate that preparations of pinocytic vesicles from rat kidney cortex can be enriched. They have biochemical characteristics that differ from those of the cell organelles and membranes previously purified from renal tissue.

Effects of hypophysectomy with or without ACTH maintenance therapy on the final steps of aldosterone biosynthesis in the rat

The effects of hypophysectomy, low-dose ACTH administration or both on aldosterone biosynthesis by incubated adrenal tissue were studied in rats during different dietary regimens. Six days after hypophysectomy without any replacement therapy, the capsular adrenals of rats receiving a complete diet converted tritiated corticosterone to aldosterone and 18-hydroxycorticosterone at a normal and at a moderately increased rate, respectively, and produced normal amounts of aldosterone from endogenous precursors. Hypophysectomy, with ACTH maintenance therapy, resulted in significant decreases in these parameters. In rats kept on a sodium-deficient diet, hypophysectomy alone did not alter the conversion rates, but led to a decreased output of endogenous aldosterone. ACTH treatment of intact as well as of hypophysectomized sodium-restricted animals was followed by a decreased incorporation of tritiated corticosterone into aldosterone and 18-hydroxycorticosterone. In rats kept on a potassium-deficient diet, hypophysectomy induced an 800 % increase in the capsular adrenal conversion of added corticosterone to aldosterone and 18-hydroxycorticosterone; this was partially prevented by ACTH treatment. Hypophysectomy with or without ACTH treatment did not impair restoration to the normal of the apparent capsular adrenal 18-hydroxylase activity in response to resumed potassium intake by potassium-restricted rats.

These results indicate that neither the maintenance nor the induction of an increased activity of the enzymes involved in the final steps of aldosterone biosynthesis due to sodium restriction or to an increased potassium intake, depend on a functioning pituitary gland. On the other hand, even small doses of exogenous ACTH, which are just sufficient for the maintenance of a normal adrenal weight in hypophysectomized animals, can cause significant decreases in the activity of these enzymes.

Effect of potassium intake on the final steps of aldosterone biosynthesis in the rat. 3. Combined sodium and potassium restriction

Capsular adrenals ("zona glomerulosa") of rats which had been kept on a sodium- and potassium-deficient diet and which were markedly hypokalaemic, converted tritiated corticosterone to 18-hydroxycorticosterone and aldosterone, and tritiated cortexolone to cortisol at the same respective rates as the capsular adrenals of sodium- and potassium-replete animals. Aldosterone production from endogenous precursors was elevated under basal conditions of incubation, but not under stimulation by added serotonin. Corticosterone and deoxycorticosterone outputs were normal during incubation with or without serotonin. Capsular adrenals of rats which had been kept first on a potassium-deficient diet for two weeks and then on a sodium- and potassium-deficient diet for two weeks converted 18 times more tritiated corticosterone to 18-hydroxycorticosterone and aldosterone and produced 5 times more aldosterone from endogenous precursors than the tissue of rats which had been kept on the potassium-deficient diet for the whole period, although the serum potassium was similarly low in both groups. These results indicate that under simple potassium restriction as well as under combined sodium and potassium restriction, neither the plasma potassium concentration nor the total body potassium is the only regulator of the activity of the enzymes involved in the final steps of aldosterone biosynthesis.

Effect of potassium intake on the final steps of aldosterone biosynthesis in the rat. I. 18-Hydroxylation and 18-hydroxydehydrogenation

Incubated capsular adrenal glands (»zona glomerulosa«) of potassiumdeficient rats converted approximately 30 times less tritiated corticosterone to aldosterone and 18-hydroxycorticosterone than capsular adrenals of potassium-replete rats. This difference was demonstrable over a large range of substrate concentrations. Capsular adrenal mitochondria of potassium-deficient rats also incorporated considerably less tritiated corticosterone into aldosterone and 18-hydroxycorticosterone than mitochondria of potassium-replete rats. Conversion to both corticosteroid fractions increased within 4 hours and became normal within 24 hours of resumed potassium intake. On the other hand, potassium intake only marginally affected the ratio of 18-hydroxycorticosterone formation to aldosterone formation by capsular adrenals and had no effect on the conversion of tritiated deoxycorticosterone to 18-hydroxydeoxycorticosterone and 18-hydroxycorticosterone by decapsulated adrenals (»zona fasciculata-reticularis« These findings indicate that potassium intake enhances 18-hydroxylase activity selectively in the zona glomerulosa of the rat adrenal cortex, but yield no information concerning an effect on 18-hydroxydehydrogenase activity. Kinetic data suggest that the potassium-induced increase in 18-hydroxylase activity is most likely due to de novo enzyme synthesis.

Effect of potassium intake on the final steps of aldosterone biosynthesis in the rat. II. 11 -hydroxylation

Incubated capsular adrenal glands (»zona glomerulosa«) of potassiumdeficient rats converted 57% less tritiated deoxycorticosterone to 11β-hydroxycorticosteroids and 45 % less tritiated cortexolone to cortisol than the capsular adrenals of potassium-replete rats. A similarly decreased conversion of cortexolone to cortisol was observed when capsular adrenal mitochondria were incubated. Potassium deficiency resulted in only a slight decrease in the rate of 11β-hydroxylation by decapsulated adrenals (»zona fasciculata-reticularis«). These findings indicate that the 11β-hydroxylase activity of the zona glomerulosa of the rat adrenal cortex is dependent on the potassium intake but to a lesser extent than 18-hydroxylase activity.

We had previously observed that potassium deficiency induced a decreased production of aldosterone, an unchanged corticosterone output and an increased deoxycorticosterone output by capsular adrenals incubated with stimulating agents. The same alterations in endogenous corticosteroid production could be induced in vitro by the addition of a selective inhibitor of 18-hydroxylation (Su 8000) to the incubation medium. On the other hand, metopirone, i.e. an inhibitor of both 11β- and 18-hydroxylation, diminished corticosterone as well as aldosterone output by capsular adrenals. These results suggest that an increased deoxycorticosterone output by capsular adrenals may be due not only to a decrease in 11β-hydroxylase activity but may also be indirectly related to a decreased conversion of corticosterone to 18-hydroxycorticosterone and aldosterone.

Quantenmechanik und Objektivierbarkeit/ Quantum Mechanics and Objective Reality

Quantum Mechanics and Objective Reality A Schrödinger function (or a density matrix) can he ascribed only to an object whose isolation time is larger than its time of revolution. This condition can never be satisfied for macroscopic bodies. Consequently, the "cut" between object and observer must not separate a macroscopic body (measuring apparatus) from the rest of the universe. Hence in an analysis of the measuring process, the state vector of the universe must be introduced. An interpretation of this state vector is given which provides an objective description of nature.

Plasma renin activity in patients with coarctation of the aorta. A comment of the pathogenesis prestenotic hypertension

In 10 patients with coarctation of the aorta, plasma renin activity was measured after recumbency and orthostatism in peripheral venous blood and, in some cases, in renal venous blood also. In nine of these patients, basic plasma renin values and those obtained under stimulatory conditions lay within normal range, and only in one patient were the values elevated. However, since this patient displayed the lowest gradient of mean arterial blood pressure proximal and distal to the stenosis, it can be regarded as improbable that the elevation in plasma renin activity was caused by the coarctation. Plasma renin activity in the renal venous blood of both kidneys, which was measured in three patients, showed no elevation.

On the basis of observations of other authors and of our own studies it can be concluded that the kidneys can contribute to the development of prestenotic hypertension in acute constriction of the aorta in experiments with animals, but in chronic coarctation in animals or in man the humoral or renal theory has no importance to the pathogenesis of hypertension.