Andres Carballeira

Conversion of steroids by chromaffin tissue I. Studies with a pheochromocytoma

Abstract Slices and homogenates of a pure pheochromocytoma have the capacity to transform C 21 steroid precursors. With suitable precursors the following reactions were obtained with the chromaffin-cell tumour preparations: hydroxylations at carbons 21, 18, 17 and 11; side chain cleavage between C 17 and C 20 ; dehydrogenation at C 3 and shifting of the Δ 5 bond to the Δ 4 position. The tumour failed to effect side chain splitting from cholesterol under different experimental conditions.

Biotransformation of progesterone-4-14C and 11-deoxy-corticosterone-4-14C by rat adrenal glands in vitro

Abstract Incubation of quartered adrenals of rats with progesterone-4-14c revealed the presence of at least 23 radioactive areas on the paper strips. Besides the four well known corticosteroids, namely, corticosterone, aldosterone, 18-hydroxycorticosterone and 18-hydroxy-11-deoxycorticosterone, evidence for the presence of 19-hydroxy-11-deoxycorticosterone, dehydrocorticosterone and 11-deoxycorticosterone is presented. 19-Hydroxy-11-deoxycorticosterone is formed predominantly in the inner zones of the adrenal. Both progesterone and 11-deoxycorticosterone are metabolized rapidly by this tissue and within 15 minutes half of the labeled precursors were transformed to other compounds.

Effects of Single Intravenous Injections of Pituitary Growth Hormone to Normal Adult Men.

Summary A highly purified preparation of pituitary growth hormone given intravenously, together with an infusion of amino acids, to 5 normal young adult men and a patient with cancer caused a consistent, rapid, sustained lowering of blood amino acid nitrogen levels and of amino acid nitrogen excretion in the urine; a rapidly occurring but transient hyperglycemia; an increase in the ketonemia of the fasting state in three subjects so studied and an increased urinary excretion of sodium-retaining material in the 2 subjects so tested. No consistent effects were noted on blood and urine phosphorus, serum alkaline phosphatase or blood eosinophiles.

Effects of aminoglutethimide, metyrapone, and ascorbic acid on testicular metabolism of cholesterol

The effects of aminoglutethimide (AG), metyrapone (MET), and ascorbic acid (AA) on the conversion of labeled cholesterol to testosterone (T) by the mature rat testis were examined and compared under identical in vitro conditions. In cell-free testicular homogenates, formation of labeled T from cholesterol-4-14C was depressed in a dose-related manner by AG and MET in concentrations ranging from 0.03 to 1.0 mM; AG was the more potent inhibitor at each concentration tested. Within this range of concentrations, AA induced a slight stimulation of the conversion of cholesterol-4-14C to T, with inhibition demonstrable only above 5.0 mM. Halfmaximal inhibition of T formation was attained with 0.1, 0.3, and 6.4 mM concentrations of AG, MET, and AA, respectively. When the synthesis of T was almost completely prevented by any of these agents, no accumulation of known intermediates between cholesterol and T could be demonstrated. Under these conditions, MET had no effect on the conversion of pregnenolone-4-14C to T or several T precursors or on the rate of metabolic degradation of testosterone-4-14C. Since the generation of the six-carbon fragment resulting from side chain cleavage of cholesterol-26-14C by rat testicular mitochondrial suspensions was also inhibited by AG, MET, and AA, the depression of steroid production affected by these agents in the testis appears to be related to their capacity to block the reaction cholesterol pregnenolone, as previously demonstrated in the adrenal and ovary. AG, MET, and AA thus inhibit cholesterol cleavage in adrenal and gonadal tissues as well as 11β-hydroxylation in the adrenal. In view of the similarities between the enzyme systems affected, it is likely that AG, MET, and AA exert their inhibitory effects on steroid-forming tissues through similar mechanisms.

Steroid biosynthesis by painted turtle (Chrysemys picta picta) adrenals

Whole homogenates and subeellular fractions of painted turtle (Chrysemys picta picta) adrenal tissue were incubated with 14C-labelled progesterone∗∗∗, pregnenolone, cholesterol. Progesterone gave rise to labelled 18-OH-B, aldosterone, cpd B, 11β-OH-P and DOC. Similar metabolites plus 14c-progesterone were obtained from pregnenolone. Cholesterol-4-14c was transformed into a variety of products ranging from pregnenolone to 18-OH-B. The presence of desmolase to cleave the cholesterol side chain between carbons 20 and 22 and 11β hydroxylase appeared to be associated with “mitochondrial” fraction. The “microsomal” and supernatant fractions showed 21-hydroxylase activity. Δ5-3β-hydroxysteroid dehydrogenase isomerase was localized in all subeellular fractions. Acetate-1-14C was not incorporated into either cholesterol or C21 steroids by surviving sections of the turtle adrenals under various experimental designs used in this study

Metabolism of Labelled Steroid Precursors by Normal Bovine Adrenal Medulla in vitro.

Summary 1) Normal bovine adrenal medulla can effect the following reactions in vitro: a) Transformation of a straight-chain precursor (acetate) into steroid tetracyclic structures; b) Double bond shifting from Δ5 to Δ4 with concomitant oxidation at C3; c) Introduction of -OH groups at specific sites of the pregnane nucleus and d) Conversion of C21 to C19 steroids. 2) It has consistently failed to metabolize cholesterol to corticosteroids. 3) It has shown in several steroid biosynthetic reactions a greater responsiveness to diphospho- and triphospho-pyridine nucleotides than the cortex.

Side-chain scission of cholesterol-4-14C by adrenocortical preincubation media (PIM) and tissue sections

Abstract Adrenal preincubation media (PIM) transform cholesterol4- 14 C into cortisol and corticosterone in absence of tissue. Supplementation is essential for cleavage activity in PIM and tissue incubates. Preformed or generated NADPH promotes similar degrees of cleavage in both preparations. NADP and 3′5′-AMP are individually operative especially in PIM. F/B ratios are higher in tissue incubates. The data indicate presence of cleavage activity in PIM and participation of the medium in the degradation of the precursor in tissue incubates.

Enzyme Activities in the Preincubation Media from Adrenal Tissue Incubations.

Summary The preincubation media, consisting of Krebs-Ringer bicarbonate glucose solution, in which well washed bovine or rat adrenal slices or sections have been incubated, have the capacity to metabolize labelled progesterone or pregnenolone when supplemented with the appropriate co-factors. The 17α-, 11β-, and 21-hydroxylase activities are activated by exogenous NADP and G-6-P, whereas the enzyme systems involved in the transformation of pregnenolone to progesterone are apparently NAD- or NADP-dependent. Enzyme activities increase in the media as time of preincubation is prolonged. Preincubation at low temperature seems to increase enzyme activities.