The functions of some CLC Cl(-) channels are evident from human diseases that result from their mutations, but the role of the broadly expressed ClC-2 Cl(-) channel is less clear. Several important functions have been attributed to ClC-2, but contrary to these expectations ClC-2-deficient mice lacked overt abnormalities except for a severe degeneration of the retina and the testes, which led to selective male infertility. Seminiferous tubules did not develop lumina and germ cells failed to complete meiosis. Beginning around puberty there was a massive death of primary spermatocytes and later also of spermatogonia. Tubules were filled with abnormal Sertoli cells, which normally express ClC-2 in patches adjacent to germ cells. In the retina, photoreceptors lacked normal outer segments and degenerated between days P10 and P30. The current across the retinal pigment epithelium was severely reduced at P36. Thus, ClC-2 disruption entails the death of two cell types which depend on supporting cells that form the blood-testes and blood-retina barriers. We propose that ClC-2 is crucial for controlling the ionic environment of these cells.

No abstract

'Classical' genomic progesterone receptors appear relatively late in phylogenesis, i.e. it is only in birds and mammals that they are detectable. In the different species, they mediate manifold effects regarding the differentiation of target organ functions, mainly in the reproductive system. Surprisingly, we know little about the physiology, endocrinology, and pharmacology of progesterone and progestins in male gender or men respectively, despite the fact that, as to progesterone secretion and serum progesterone levels, there are no great quantitative differences between men and women (at least outside the luteal phase). In a prospective cohort study of 1026 men with and without cardiovascular disease, we were not able to demonstrate any age-dependent change in serum progesterone concentrations. Progesterone influences spermiogenesis, sperm capacitation/acrosome reaction and testosterone biosynthesis in the Leydig cells. Other progesterone effects in men include those on the central nervous system (CNS) (mainly mediated by 5alpha-reduced progesterone metabolites as so-called neurosteroids), including blocking of gonadotropin secretion, sleep improvement, and effects on tumors in the CNS (meningioma, fibroma), as well as effects on the immune system, cardiovascular system, kidney function, adipose tissue, behavior, and respiratory system. A progestin may stimulate weight gain and appetite in men as well as in women. The detection of progesterone receptor isoforms would have a highly diagnostic value in prostate pathology (benign prostatic hypertrophy and prostate cancer). The modulation of progesterone effects on typical male targets is connected with a great pharmacodynamic variability. The reason for this is that, in men, some important effects of progesterone are mediated non-genomically through different molecular biological modes of action. Therefore, the precise therapeutic manipulation of progesterone actions in the male requires completely new endocrine-pharmacological approaches.

The mechanisms responsible for the initial transport of immotile sperm from the testis into the epididymis are still poorly understood. We show here by electron microscopy and immunohistochemical approaches that the tunica albuginea of the human testis contains abundantly contractile elements. This tissue is also distinguished by extraordinarily high concentrations of cyclic GMP (cGMP)-dependent protein kinase I, known to mediate cGMP-dependent relaxation. Atrial natriuretic peptide (ANP) and the nitric oxide donor sodium nitroprusside (SNP) increased cGMP production in isolated strips of the tunica, and the enzymes involved could be demonstrated by affinity cross-linking and immunological techniques. Contractile cells as well as ectopic Leydig cells were identified as sites of nitric oxide synthase expression. Physiological studies revealed spontaneous contractions exclusively in regions near the rete testis. These contractions could be attenuated but not abolished by cGMP, SNP, and ANP. Remarkably, SNP reduced only the amplitudes, whereas ANP in addition decreased the frequency of these contractions. In contrast, noradrenaline-induced contractions, detectable in all parts of the capsule, could be abolished completely by SNP. These data, demonstrating complex contraction and relaxation activities, are indicative of a major physiological role of the tunica albuginea presumably related to testicular sperm transport.

Despite a rapidly increasing acceptance for a role of ATP as an extracellular mediator in several biological systems, the present report shows The role of nucleotides in metabolism is well established, but recognition of their potential importance as extracellular transmitters, regulators or modulators has been very recent. Extracellular ATP has been shown to induce a variety of responses, such as stimulation of inositol phospholipid turnover and activation of membrane conductances in many cell types and preparations (1-4). These responses are now known to be mediated by a family of ATP receptors, designated P2 purinoceptors (5-7), some of which have been cloned (8-11). ATP has been shown to stimulate inositol phosphate accumulation and intracellular Ca2+ metabolism in pituitary cell cultures (12), and our own data from fetal hypothalamic neuron cultures suggests that ATP has a possible regulatory role in the neuroendocrine system (13). Recently we have shown that ATP and UTP act on ATP receptors to provoke a rapid and dramatic increase in cytosolic Ca2+ in pituitary gonadotropin-release hormone (GnRH)-responsive cells (14). Using a superfusion system to examine the functional effect of extracellular nucleotides on the kinetics of pituitary hormone secretion and using real-time dynamic bioluminescence measurements of ATP, we now demonstrate that ATP receptors can mediate significant release of pituitary gonadotropin and that ATP can be exocytotically released from pituitary cells.The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.MATERIALS AND METHODS Materials. Collagenase was purchased from Serva; medium M199, Ca2+-free Hanks' balanced salt solution, and sera were from GIBCO/BRL; GnRH and A23187 were from Calbiochem; and 2-methylthio-ATP and adenosine 5'-[3,y-methylene]triphosphate (13,y-methylene-ATP) were from Research Biochemical International (Natick, MA). Bromo-A23187, highly purified nucleotides, and all others, unless otherwise stated, were obtained from Sigma. Superfusion of Pituitary Cells. Pituitary glands from4-week-old female Wistar rats were enzymatically dispersed in medium M199 containing bovine serum albumin (BSA; 0.3%), collagenase (1 mg/ml), hyaluronidase (0.5 mg/ml), and DNase (25 ,ug/ml) as described (15). Aliquots of the cell suspension containing -3-4 x 106 cells were plated out on a 12-well culture plate containing 15 mg of Cytodex I beads, which had been preswollen in phosphate-buffered saline and autoclaved. Superfusion experiments were performed as described (15). After 2 days in culture, cells and beads were transferred to superfusion columns (5 x 25 mm Bio-Rad Econocolumns) and superfused with medium M199 containing 0.3% BSA, 1.8 mM Ca2+, 2 mM glutamine, and 20 mM Hepes at 37°C at the rate of 0.65 ml/min. A 90-min superfusion was carried out to wash cells before the start of superfusate collection. Superfusate fractio...