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N W Leveque

Publications and source records attributed to N W Leveque.

7 recordsLinked to original sources
PubMed1984

Quantitation of LH subunits released by rat anterior pituitary cells in primary culture.

Immunoreactive rLH, rLH alpha, rLH beta and rFSH in the cell extracts and medium of rat anterior pituitary cell cultures were measured after gel filtration on Sephadex G-100 Superfine. Cell extracts contained uncombined rLH alpha and rLH beta present as approximately 40% and 4%, respectively, of native rLH on a molar basis. Unstimulated cultures appeared to release a large excess of rLH alpha (approximately 2560% of rLH on a molar basis) as well as a minimum of uncombined rLH beta. Stimulation of cultures with physiological (LHRH) or non-physiological agents (A23187, elevated K+) increased the absolute but not the relative quantities of uncombined subunits released relative to those present intracellularly. Thus, rat anterior pituitary cell cultures appear to produce and release an excess of free alpha subunit as well as a minimum of uncombined rLH beta. However, one cannot be certain whether the uncombined rLH beta represents a pool of 'free' rLH beta or simply results from the dissociation of rLH.

Animals↗
PubMed1984

Effects of various secretagogues on gonadotropin release by rat anterior pituitary cell cultures.

Rat anterior pituitary cell cultures were utilized to compare LH and FSH release induced by LHRH, cAMP derivatives, cGMP derivatives, the calcium ionophore A23187, and elevated K+. Of the cyclic nucleotide derivatives tested, only 8-Br-cAMP released significant quantities of both LH and FSH. A23187 and elevated K+ released significant quantities of LH and FSH but supramaximal concentrations of these stimuli liberated only approximately 50% of the gonadotropins released by LHRH. Thus, none of the secretagogues tested was as efficacious as LHRH in releasing either LH or FSH.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1982

Testosterone inhibition of LRH-induced luteinizing hormone release by cultures of rat anterior pituitary cells: effect of inhibitors of steroid 5 alpha reductase.

Cultures of rat anterior pituitary cells were utilized to examine the role of 5 alpha reduction in the inhibitory action of testosterone on LRH-induced LH release. Cultures were pre-treated with steroids for 48 h and then incubated 6 h with steroids plus 5 x 10(-10) M LRH, the approximate EC50 for LH and FSH release. Testosterone inhibited LRH-induced LH release with an IC50 of approximately 2 x 10(-10) M. However, even relatively high concentrations of testosterone did not completely inhibit LRH-induced release. Testosterone (and dihydrotestosterone) appeared to antagonize LRH-induced LH release but did not markedly affect 48 h basal release or LH synthesis as judged by the quantity of LH released plus that remaining intracellularly. Progesterone (10(-6) M) and heparin (1000 U/ml) were used as inhibitors of anterior pituitary steroid 4 alpha reductase. Progesterone, when combined with testosterone, markedly shifted the testosterone inhibition curve to the right (approximately 340-fold) but did not shift the dihydrotestosterone inhibition curve. Heparin also slightly shifted the testosterone inhibition curve (approximately 2.4-fold) to the right. These observations support the hypothesis that the mechanism of action of testosterone on the anterior pituitary involves 5 alpha reduction.

5-alpha Reductase Inhibitors↗