PULSATILE RELEASE OF GONADOTROPINS IN YOUNG PONY STALLIONS
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abstract
Basal concentrations and pulsatile-release patterns of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were characterized in five pony stallions, aged 2 to 4 yr. Jugular blood was collected from each pony at 20-min intervals for 24 h. Plasma was separated and frozen until quantification of LH and FSH by RIA. Hormonal data were subjected to a computerized cycle-detection program for estimating frequency and amplitude of regular and irregular episodic fluctuations in gonadotropin concentrations in the presence of high levels of random measurement errors. Ponies were castrated, testes were weighed, and parenchymal sections were procured for determination of daily spermatozoal production per gram of testicular parenchyma (DSP/gm) and daily spermatozoal production per pony (DSP). Values (mean SD) for basal concentration of LH (basal LH), LH pulse amplitude (amp LH), duration of LH pulse (dur LH), LH pulse frequency (freq LH), basal concentration of FSH (basal FSH), FSH pulse amplitude (amp FSH), duration of FSH pulse (dur FSH), and FSH pulse frequency (freq FSH) were 4.80 2.39 ng/ml, 3.13 1.16 ng/ml, 46.4 3.6 min, 0.869 0.04 pulses/h, 7.34 6.33 ng/ml, 6.50 7.60 ng/ml, 43.9 11.7 min, and 0.868 0.14 pulses/h, respectively. Regression analyses revealed significant (P<0.05) linear relationships between freq LH and DSP/gm (r=0.97), basal LH and DSP/gm (r=0.89), amp LH and DSP (r=0.99), freq LH and DSP (r=0.97), and basal LH and DSP (r=0.92). A significant quadratic relationship existed between amp LH and DSP/gm (r=0.99). Both amp LH and freq LH were more highly correlated with DSP/gm and DSP than was basal LH. Basal concentrations and pulsatile release characteristics of LH were not related to testes weight (TW) (P>0.05). Morever, basal concentrations and pulsatile release characteristics of FSH were not related to TW, DSP/gm or DSP (P>0.05). Cross-correlations between LH and FSH were not observed (P>0.05). 1990.
