Two experiments were conducted, the first to compare sperm output and the second to determine serum testosterone in rabbits given PGF2α or PGE2. In the first, six rabbits were ejaculated twice each Monday, Wednesday and Friday for 5 weeks. Each rabbit was given subcutaneously (sc) each of the following treatments five times: 1) saline, 2) 5 mg PGF2α and 3) 5 mg PGE2. Treatments were given, half at 4 hr and half at 2 hr before first ejaculations. Both PGF2α and PGE2 caused increased (50% and 84%) sperm content of first ejacula, without significantly altering characteristics of second ejacula. The extra sperm in first ejacula was a function of increased sperm density, because seminal volume was unaltered. In the second experiment, 15 rabbits were bled at 0.5-hr intervals for 9 hr and given (sc): 1) saline at 1 and 3 hr (n=4), 2) 2.5 mg PGF2α at 1 and 3 hr (n=4), 3) 2.5 mg PGE2 at 1 and 3 hr (n=4) or 4) 5 mg PGF2α at 1 hr after the onset of blood sampling. In saline-treated controls, episodic surges of testosterone occurred on the average every 5 hours. After the injection of 2.5 or 5.0 mg PGF2α, serum testosterone began to rise at 0.5 hr, peaked (8 to 13 ng/ml) at 1 hr and approached a nadir (0.5 ng/ml) within 4 hours. The second injection of 2.5 mg PGF2α failed to significantly affect serum testosterone. PGE2 treatment was followed by significantly depressed serum testosterone; only 1 of these 4 rabbits had any surge of testosterone for the 8 hr after treatment. In conclusion, PGF2α and PGE2 both increased sperm output, but PGF2α increased serum testosterone while PGE2 depressed serum testosterone. Thus, the sperm output effect of these prostaglandins probably is independent of the acute changes in testosterone secretion.
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