Sie befinden Sich nicht im Netzwerk der Universität Paderborn. Der Zugriff auf elektronische Ressourcen ist gegebenenfalls nur via VPN oder Shibboleth (DFN-AAI) möglich. mehr Informationen...
1 Division of Biology of Growth
and Reproduction, Department of Pediatrics, University of Geneva
School of Medicine, 1211 Geneva 14, Switzerland; and
2 Department of Physiology,
Institute of Biomedicine, University of Turku, 20520 Turku, Finland
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 µg/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.
luteinizing hormone; pulsatile secretion