Influence of Sexual Stimulation and the Administration of Human Chorionic Gonadotrophin on Plasma Testosterone Levels in Dogs

Abstract

The influence of sexual stimulation and human chorionic gonadotrophin (hCG) administration on plasma testosterone concentrations was assessed in five male Beagles. Each dog was exposed to three experimental treatments: C treatment (Control, no stimulation), hCG treatment (dogs were SC injected with 1000IU of hCG) and sexually stimulated (SS) treatment where semen was collected from the males. All dogs were exposed to all treatments, one per week for three consecutive weeks, with a 1week of rest between treatments. Blood samples were taken with the same time intervals (0, 10, 30, 60 and 120min) relative to treatments. Plasma testosterone concentrations were determined with a solid-phase I 125 radioimmunoassay. In the control treatment, the testosterone plasma levels did not show significant changes throughout the tested period (mean values ranging between 2.8 and 4.7ng/ml); the hCG group presented a significant increase (p<0.05) in plasma testosterone levels 30min after hCG administration and had the highest value (8.7ng/ml) at 120min post-hCG. Finally, the SS group revealed a slight reduction in testosterone concentration immediately after ejaculation, but the values remained nearly unaltered until 120min after semen collection. When the groups were compared, the hCG group showed higher plasma testosterone values (p<0.05) than did the C and SS groups, starting at 30min and continuing until the end of sampling. This study demonstrates that sexual stimulation associated with semen collection does not produce transitory modifications in plasma testosterone concentrations. © 2011 Blackwell Verlag GmbH.