Many LH peaks are needed to physiologically stimulate testosterone secretion: modulation by fasting and NPY

Article Article scientifique Article Many LH peaks are needed to physiologically stimulate testosterone secretion: modulation by fasting and NPY eng 1999 author Pierroz DD author Aebi Anne Catherine 33450 author Huhtaniemi IT author Aubert Michel 25310 E603-610 10.1152/ajpendo.1999.276.4.E603 10198294 0002-9513 http://ajpendo.physiology.org/content/276/4/E603.long The pulsatile luteinizing hormone (LH) and testosterone secretions were studied during serial blood collections performed at 7-min time intervals in the male rat. In fed rats, a discontinuous pattern of LH secretion was observed. Periods without secretion alternated with active secretory episodes consisting in trains of three to four LH peaks that triggered testosterone secretion usually 1-2 h later. The magnitude of the testosterone response was not correlated with the amplitude of the LH peaks. Isolated, single peaks of LH did not evoke clear testosterone responses. Forty-eight hours after initiation of fasting, testosterone secretion was markedly decreased, but integrated LH secretion was only partly reduced. Chronic infusion of neuropeptide Y (NPY; 18 microgram/day, icv) reduced testosterone secretion to very low levels and abolished pulsatile LH secretion or testosterone response to isolated LH peaks. In conclusion, the stimulation of testosterone secretion by LH necessitates several LH peaks organized in a proper sequence, and the testosterone response is not immediate. Low testosterone secretion in fasting rats appears to result from disappearance of coordinated, multiple LH peaks of sufficient size. Inhibition of the gonadotropic axis achieved by central NPY administration is due to either absence of LH peak "clusters" or occurrence of nonfunctional single LH peaks. Activity Cycles Animals Cerebral Ventricles/drug effects/physiology Fasting/physiology Homeostasis Infusions, Parenteral Luteinizing Hormone/blood/secretion Male Neuropeptide Y/administration & dosage/pharmacology Organ Size/drug effects Rats Rats, Sprague-Dawley Seminal Vesicles/drug effects/physiology Testis/drug effects/physiology Testosterone/blood/secretion Dewey 618 58 Département de pédiatrie, gynécologie et obstétrique 223 false The American journal of physiology 276 4 Pt 1 dcd1ed77-a16a-4bdf-902f-ff1cd4665966 Article (Published version) Public 603-610.pdf 197076 application/pdf openAccess Faculté de médecine / Section de médecine clinique / Département de pédiatrie, gynécologie et obstétrique

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Many LH peaks are needed to physiologically stimulate testosterone secretion: modulation by fasting and NPY	The American journal of physiology			1999	498	472

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Aebi, Anne Catherine