Mechanical response in the wall of ovarian follicles mediated by adrenergic receptors

The identity of the adrenergic receptors involved in the contractility of the follicular wall was studied in bovine ovaries. Strips were prepared mainly from the protruding part of large Graafian follicles and mounted in an organ bath for recording of mechanical activity. Some intact ovaries and strips from the bottom of follicles were also studied. The latter two preparations showed spontaneous rhythmic contractions, and the tension was increased by norepinephrine and reduced by terbutaline. Norepinephrine, epinephrine, phenylephrine, isoproterenol and terbutaline alone or in combination with various concentrations of the inhibitors, phenoxybenzamine, piperoxan and propranolol, were used to analyze adrenoceptors in strips from the protruding portion of the follicle. Such strips showed no appreciable spontaneous contractions. A contractile response was found to be mediated by alpha receptors. The KA value for norepinephrine (determined in combination with phenoxybenzamine) was found to be 2.26 X 10- minus 6 M and KB for piperoxan (determined in combination with norepinephrine) was 1.02 X 10-minus 8 M (pA2 = 8.19). Adrenergic beta receptors mediated relaxation of the strips, and the KB value for propranolol (determined in combination with terbutaline) was 7.28 X 10-minus 9 M (pA2 = 8.17).