Rate of oxidative and glycolytic metabolism in the guinea-pig oviduct in relation to contractility and hormonal cycle
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The rates of oxygen consumption and lactate production in the guinea-pig oviduct were measured together with registration of contractile activity during three phases of the hormonal cycle. In pro-oestrus (high oestrogen, low progesterone levels) and oestrus (time of ovulation, high oestrogen and progesterone) the rate of O2 consumption was higher than in dioestrus (low oestrogen, high progesterone). The frequency of spontaneous contractions was higher in oestrus than in the other phases. No significant differences in the proportion of the cross-sectional area occupied by smooth muscle were found between oviducts in di- and pro-oestrus. Stimulation by phenylephrine caused decreased frequency and increased amplitude of contractions in dioestrus but not in pro-oestrus, suggesting hormonal modulation of adrenergic mechanisms. The rate of relaxation of high-K+ contractures was higher in pro- than dioestrus. Lactate production and contents of ATP, ADP and phosphocreatine showed no significant variation with hormonal state. The increased rate of oxidative metabolism under oestrogenic dominance could in part reflect changes in ionic transport mechanisms, such as intracellular Ca2+ handling.