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

Abstract

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.

The Influence of Gibberellic Acid on the Permeability of Model Membrane Systems

“…The physiological significance of steroid-induced changes in membrane permeability is presently thought to be most closely associated with hormonal effects on lysosomes (19). Close similarities in in vivo and in vitro effects strongly support the contention (3).…”

Steroid-Protein Binding: from Circulating Blood to Target Cell Nucleus

“…Moreover, labilization of the integrity of membrane-bound compartments may, as occasionally suggested [43,79,84], underlie the apparent 'induction' of specific proteins, as judged by the incorporation of radioactivity from isotopic amino acids, in estrogenic targets by the hormone applied in vivo [43,47,89] and in vitro [36,43]. Both enhanced transport of amino acid precursor [61] as well as concomitant liberation of proteinases and other acidic proteins from target-specific lysosomes, where these products occur in structurally latent form [94], would be ex pected to contribute to increased incorporation of isotope, through aug mented turnover, into the proteins thus solubilized in the presence of the hormone (cf. also [93]).…”

“…The covert labilization of lysosomes by exposure to hormone in vivo [94] or to cyclic nucleotide in vitro [82], with consequent liberation of solubilized proteins, can be demonstrated readily by analyses of the in cubation or extraction medium for characteristic hydrolases whose struc tural latency is thus reduced [6,82,94]. For these reasons, and for others discussed elsewhere [85], it is implicit in the above observations that pro teins of the appropriate hormone avidity, which occur as integral portions of the target cell membrane and which are thus capable of intercepting and binding the agonist and consequently promoting its internalization by micropinocytosis [85], may likewise owe their origin, presumably by exocytosis [56] to site-specific lysosomes.…”

“…28], Because of our long preoccupation with the problem of membranebound compartments in hormone action and the influence of hormones in reducing such barriers as a triggering mechanism for the propagation of secondary effects [78], we turned to the lysosome as having properties which fulfilled a number of these requisites [79], For many of these studies we utilized the preputial gland, a target organ for steroid hormones of both sexes [21] and greatly enriched in lysosomal enzymes [4], However, paral lel data were obtained when uterus served as the source of lysosomes. Lysosomes were isolated in highly purified form by relatively nondestruc tive7 * procedures of cell disruption from these organs of the ovariectomized rat [94]. Particle-free proteins were then solubilized from the organelles by a variety of procedures and analyzed for their interaction with [3H]-cstradiol-17/?.…”

“…2). The mean association constant and its standard error for the high-affinity binding from a series of five similar experiments analyzed by a rigorously controlled dextrancoated charcoal method [28] [94] were isolated from preputial glands of Sprague-Dawley rats that had been maintained in a low-steroid environment for 3 weeks after ova riectomy. Soluble 'lysosol' components were obtained by stirring for 2 h at 4 °C in the presence of 0.054 m sodium phosphate buffer, pH 7.7, followed by centrifuga tion at 105,000 g at 0 °C.…”