Date of Award:

5-1-1975

Document Type:

Dissertation

Degree Name:

Doctor of Philosophy (PhD)

Department:

Biology

Department name when degree awarded

Biology

Committee Chair(s)

LeGrande C. Ellis

Committee

LeGrande C. Ellis

Committee

Jay W. Call

Committee

Warren C. Foote

Committee

Raymond T. Sanders

Committee

Raghubir P. Sharma

Abstract

The frequency and depth of contractions of seminferous tubules from the rat, rabbit, hamster, mouse and squirrel were studied in vitro. Although the contractions were greater in the rat, all the animals had some degree of activity. The contractile activity of a seasonal breeder, the Uinta ground squirrel (Spermophilus armatus), was examined. The diameter of the tubules and the contractility were greater prior to emergence from hibernation and declined markedly during and after the breeding season. Several pharmacological studies were conducted on tubules of the rat. Oxytocin caused an increase in the contractile frequency while progesterone inhibited the frequency in a dose-dependent manner. Prostaglandin F1⍺ stimulated the frequency of the contractions at all concentrations tested (10-8M to 10-5M) but little change was noted in the depth. The diameter of the tubules was decreased by this treatment, indicating that the tonus of the smooth muscle cells surrounding the tubules was increased by prostaglandin F1⍺. Treatment of the tubules with prostaglandin E1 produced a bimodal response. At a low concentration (10-9M), a stimulation of the contractile frequency and a decrease in the diameter of the tubule was noted. As the concentration was increased to I0-7M and I0-6M, the frequency and depth of the contractions were inhibited. As the effect of the E-type prostaglandins on smooth muscle may be mediated through cyclic AMP, the effect of this compound on tubular contractility was examined. Intratesticular implants of both cyclic AMP and dibutyryl cyclic AMP inhibited the depth of the contractions and the frequency and also increased the diameter of the tubules. Treatment of the tubules with solutions of dibutyryl cyclic AMP (2 mM) and theophylline (0.05 mM), a phosphodiesterase inhibitor, resulted in responses similar to the implants. The synthesis of prostaglandins is inhibited by the antiinflammatory agent indomethacin. Injections of this compound (10 mg/kg) for 2 days prior to examination of the tubules produced a decrease in the frequency of the contractions, but this decrease only approached significance. When these tubules were placed in a solution of indomethacin (10 µg/ml) for 1½ hours, a significant decrease in the contractile activity was observed. Further, when the tubules from animals pretreated with indomethacin were placed in the indomethacin solution for 1½ hours, the degree of inhibition of contractility was more pronounced. In an additional experiment, the bathing solution was removed from contracting tubules and these tubules were rinsed several times with fresh Tyrode's solution. This procedure decreased tubular contractility. Contractility was restored when the original bathing solution was added back to the tubules. Also, daily injections of the antigonadal hormone melatonin from the pineal gland inhibited the frequency and depth of tubular contractions.

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