Biology of Reproduction, Vol 19, 217-222, Copyright © 1978 by Society for the Study of Reproduction

Inhibitory Effects of Melatonin, Prostaglandin E₁, Cyclic Amp, Dibutyrylcyclic AMP and Theophylline on Rat Seminiferous Tubular Contractility in vitro

¹ Department of Biology UMC 53, Utah State University, Logan, Utah 84322 and Department of Zoology Ricks College Rexburg, Idaho

Autorhythmic contractions (frequency) of seminiferous tubules from adult male rats responded biphasically to PGE₁ in vitro. At low concentrations (10^-9 M), the frequency increased, but at higher concentrations (10^-7 or 10^-8 M), the rate of contractions was diminished. Depth or intensity of tubular contractions showed a similar trend with a decreased magnitude at 10^-6 M. Tonus of the tubules was increased at 10^-9 M concentration of PGE₁, but not at higher concentrations. Silastic implants of either cyclic AMP or dibutyryl cyclic AMP decreased contractility of rat seminiferous tubules in vitro as did the incubation of seminiferous tubules with dibutyryl cyclic AMP (2 mM) and theophylline (2.8 x 10^-4 M). Subcutaneous injections of melatonin (250, 500 and 1,000 µg/day) also diminished both the frequency and depth of contractions, but not tonus of siminiferous tubules. It was concluded that cyclic AMP could be a second messenger for PGE₁, but not for melatonin.

Note:
ACKNOWLEDGMENTS Appreciation is extended to Utah State University Research for their support of this research through project U-300. We thank Dr. John E. Pike of the Upjohn Co. for the generous gift of prostaglandins.