Concerning possible mechanisms of hormone action

Effect of some polypeptide hormones on the lateral mobility in plasma membranes of rat testes, L-cells and liver. Influence of development and ageing

1. The effect of different doses of six polypeptide hormones on pyrene diffusion in rat testes and liver plasma membranes was tested. Pyrene mobility was reduced in membranes possessing respective receptors. 2. An incubation time of 15 min of testes plasma membranes with 10(-5) M lutropin (LH) reduced pyrene and diphenyl hexatriene mobilities by 10-20%. 3. The addition of 10(-5) M LH to a suspension of intact L-cells from rats at different ages decreased the diffusion of membrane fluorescently labelled lipids and proteins by ca 60%. Diffusion was measured by fluorescence recovery after photobleaching. 4. Observed LH effects were independent of development and ageing.

Detection in bovine adrenal cortex of a lipoidal substance that yields pregnenolone upon treatment with alkali

Bovine adrenal cortical tissue contains a lipoidal derivative of pregnenolone (3beta-hydroxy-pregn-5-en-20-one) from which the free steroid can be liberated by treatment with alkali. Evidence for the presence of such an entity comes from examination of a nonpolar extract of tissue from which pregnenolone and its sulfate had been removed by chromatography. Treatment of the nonpolar fraction with alkali followed by exhaustive chromatographic analysis led to the detection of pregnenolone. The steroid was identified by both gas chromatography/mass spectrometry and double isotope procedures. Quantitative analysis indicated that the three forms of pregnenolone are present in bovine adrenal cortical tissue in the following amounts (mug/kg): lipoidal derivative, 290; free steroid, 435; and sulfate, 65. Because the only known metabolic function of pregnenolone is to serve as a precursor of the steroid hormones, these findings have far-reaching implications for steroid hormone biochemistry.

The lysosomal membrane complex. Focal point of primary steroid hormone action

At short intervals after the intravenous administration of oestradiol-17beta, diethylstilboestrol, testosterone or saline control solution to ovariectomized rats, highly purified lysosome samples were prepared in substantial yield from preputial glands, sex accessory organs rich in these organelles. The preparations were essentially devoid of mitochondrial contamination. Exposure in vivo to doses of these hormones varying from 0.1 to 5mug/100g body wt. provoked dose-dependent labilization of the lysosomal membrane surface, as evidenced by significantly diminished structural latency of several characteristic acid hydrolases, including acid phosphatase, beta-glucuronidase and acid ribonuclease II, when such preparations were subsequently challenged in vitro with autolytic conditions, detergent or mechanical stress. Enhanced lytic susceptibility induced by hormone pretreatment was occasionally detectable in the initial preparation without further provocative stimuli in vitro. Comparable results were obtained with the corresponding fractions of uterus, despite the more limited concentration of lysosomes in this steroidal target organ. By the present criteria oestradiol-17alpha was essentially inert, even in a dose 25 times that effective for its active beta-epimer (<0.1mug/100g body wt.). Pretreatment with diethylstilboestrol exerted substantial membrane-destabilizing influence in preputial-gland lysosome samples from orchidectomized rats. Moreover, administration of testosterone to gonadectomized animals resulted in essentially equivalent dose-dependent augmentation of lysosomal enzyme release in preputial-gland preparations of either sex. The membrane stability of lysosome-enriched preparations from uterus, on the other hand, was unaffected by testosterone pretreatment. The sensitivity, specificity and selectivity of the lysosomal response to sex steroids provide evidence for the physiological significance of this phenomenon as a general mechanism for mediation of secondary biochemical transformations in the hormone-stimulated target cell.

In Vitro Effects of Estradiol on the Aorta of Chickens

Aortas of chickens were incubated during 72 hours with 17α- or with 17β-estradiol and the alkaline phosphomonoesterase activity determined. Paired experiments demonstrated that both isomers are able to enhance the activity of the enzyme in vitro. The possible relation of these results with atherogenesis is discussed.

Alteration by dinitrocresol of pathways for glucose oxidation in eggs of arbacia punctulata

1. The C(14)O(2) production by Arbacia eggs and embryos from glucose-1-C(14), glucose-2-C(14), and glucose-6-C(14) has been measured without and with dinitrocresol in the incubation medium. In the absence of the dinitrocresol, the C(14)O(2) production from glucose-1-C(14) is more rapid than from glucose-2-C(14) and much more rapid than from glucose-6-C(14); this, together with previous findings, indicates that glucose is utilized in Arbacia eggs predominantly via the TPN shunt rather than via the aldolase step of the glycolytic pathway. In the presence of the dinitrocresol, C(14)O(2) from glucose-6-C(14) approaches that from glucose-1-C(14), indicating that, in the presence of this reagent, glucose utilization is diverted from the shunt to the glycolytic pathway. 2. Incorporation of C(14) from glucose labelled in the 1-, 2-, or 6- positions into other metabolic products of the eggs and embryos is also inhibited by dinitrocresol, particularly incorporation into the acid-insoluble fraction containing nucleoproteins.