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Angiotensin II (ANG II) is the most potent and the most physiologically important stimulator of aldosterone synthesis and secretion from the adrenal zona glomerulosa. Because steroidogenesis by adrenal glomerulosa (AG) cells is mediated in part by Ca2+ influx through T- and L-type Ca2+ channels, we evaluated whether T-type Ca2+ channels are regulated by ANG II. We observe that ANG II enhances T-type Ca2+ current by shifting the voltage dependence of channel activation to more negative potentials. This shift is transduced by the ANG II type 1 receptor. The effect of the hormone is not mediated by Ca2+/calmodulin-dependent protein kinase II (CaMKII) as it is not prevented by CaMKII(281-302), a peptide inhibitor of the catalytic region of the kinase. Rather, this shift is mediated by the activation of a G protein, Gi, because it is abolished by cell pretreatment with pertussis toxin and by cell dialysis with a monoclonal antibody generated against recombinant Gi alpha. This effect of ANG II on T-type Ca2+ channels should increase Ca2+ entry in AG cells at physiologically relevant voltages and result in a sustained increase in aldosterone secretion.

Constitutively active nitric oxide synthases (NOS) are a unique class of NADPH-dependent, calcium/ caimodulin-dependent enzymes that catalyze the conversion of L-arginine to nitric oxide and L-citrulline. However, little is known about the molecular similarities or differences between the two prototypical constitutive NOS enzymes, endothelial NOS (ECNOS) and brain NOS (bNOS). The aims of this study were to begin characterizing the gene structure and tissue distribution of messenger RNAs (mRNAs) for ECNOS and bNOS and to examine the immunological resemblance of the proteins by Western blotting. Full-length complementary DNAs (cDNAs) encoding bovine ECNOS and rat bNOS hybridized, under high stringency, to different-sized fragments of endonuclease-digested bovine, rat, and human genomic DNA. In addition, more than one fragment was detected with both cDNAs, suggesting that ECNOS and bNOS genes contained multiple introns. Tissue distribution of ECNOS mRNA (4.4 kb) and bNOS mRNA (9.5 kb) in the rat was detected by Northern blotting. Patterns among tissue extracts were strikingly different, with ECNOS mRNA being most abundant in aorta, heart, lung, kidney, adrenal gland, spinal cord, and urogenital tissues and bNOS mRNA most prominent in brain regions, intestine, stomach, spinal cord, adrenal gland, and aorta. Interestingly, ECNOS cDNA detected two equally abundant RNA transcripts (4.4 and 4.0 kb) in most brain regions tested, suggesting an alternative splicing of the ECNOS pre-mRNA. Western blotting, using an ECNOS monoclonal antibody, recognized ECNOS protein from native bovine endothelial cells, cultured bovine endothelial cells, and COS cells transfected with ECNOS cDNA but did not recognize purified bNOS. Collectively, these data demonstrate that ECNOS and bNOS are encoded by different genes, expressed in distinct but overlapping tissues, and are immunologicaHy different proteins. (Hypertension 1993^1:934-938) KEY WORDS • nitric oxide • blotting, Northern • RNA • genes T he nitric oxide synthase (NOS) family of proteins represents a novel class of mammalian enzymes that converts L-arginine to nitric oxide and L-citrulline. NOS are unique proteins inasmuch as they contain protoporphyrin iron characteristic of cytochrome P-450 hemoproteins 1 and cofactor binding domains for flavin adenine dinucleotide, flavin mononucleotide, and NADPH as seen in cytochrome P-450 reductase.2 To date, several isoforms of NOS have been isolated and characterized based on subcellular localization and calcium dependence of enzymatic activity.3 Molecular cloning of brain NOS (bNOS), 2 macrophage NOS, 4 -6 and, most recently, endothelial NOS (ECNOS) 7 -10 demonstrates approximately 50% identity among the deduced proteins, From the Departments of Physiology

Gonadotropin-releasing hormone (GnRH) receptor antagonists have potential in treating numerous hormone-dependent pathologies including cancers of the prostate, breast, and ovary, endometriosis, and fertility disorders. An unmet clinical need exists for an orally available GnRH receptor antagonist. Guided by structure-activity relationships, ligand-based targeted library designs, and biomarker measurements, our discovery efforts have yielded a novel, small molecule GnRH receptor antagonist, 5- [(3,5,5,8,8-pentamethyl-5,6,7,8-tetrahydro-2-naphthalenyl)methyl]-N-(2,4,6-trimethoxyphenyl)-2-furamide (CMPD1). CMPD1 bound with low nanomolar affinities to human, rat, and mouse GnRH receptors (6.0, 3.8, and 2.2 nM, respectively). CMPD1 was more than 100-fold selective for GnRH receptors versus various G-protein-coupled receptors and other enzymes and ion channels. In cells expressing recombinant rat GnRH receptors, CMPD1 was a competitive antagonist of GnRHstimulated increases in extracellular acidification rates in Cytosensor microphysiometer assays. In cells expressing recombinant human GnRH receptors, CMPD1 was a potent inhibitor of GnRH-stimulated total inositol phosphate accumulation. The effects of CMPD1 on circulating levels of luteinizing hormone (LH) and testosterone were studied in castrated and intact male rats, respectively. Intravenous and oral administration of CMPD1 dose dependently suppressed GnRH-mediated elevations of LH in castrated male rats and testosterone in gonadintact male rats. Moreover, CMPD1, when given at 20 mg/kg i.v. to intact male rats, inhibited the elevations of LH and testosterone stimulated by the superagonist of GnRH, [D-Ala 6 , desGly 10 ]GnRH (GnRH-A). These data suggest that CMPD1 is a potent, selective, orally active GnRH receptor antagonist that may have potential application as a therapeutic agent for treating hormone-dependent cancers and diseases.Gonadotropin-releasing hormone (GnRH) is a neuroendocrine decapeptide (pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-ProGly-NH 2 ) synthesized in the neurovascular terminals of the hypothalamus and is secreted in a pulsatile manner directly into the hypophyseal portal blood supply. GnRH selectively binds specific receptors on the membranes of the anterior pituitary gonadotroph cells to stimulate synthesis and release of the gonadotropic hormones [luteinizing hormone (LH) and follicle-stimulating hormone (FSH)]. LH and FSH stimulate gonadal production of sex steroids and gametogenesis, respectively. GnRH, as the primary regulator of LH, is consequently the primary regulator of the sex hormones testosterone and estrogen. GnRH and its analogs have stimulated much interest because of their potential therapeutic benefit in treating sex hormone-dependent diseases such as prostate, ovarian, and breast cancer, as well as endometriosis, uterine fibroids, benign prostate hyperplasia, fertility disorders, and precocious puberty (Huirne and Lambalk, 2001). In contrast to GnRH agonists, which are associated with an initial surge in LH and testosterone ...