THE EFFECTS OF PROGESTERONE ON GLUCOSE AND LACTATE METABOLISM IN OVARIECTOMIZED SHEEP

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Abstract
In 9 samples from 4 ovariectomized sheep the mean plasma concentration of progesterone was 0.19 .+-. 0.4 ng/ml. After the s.c. implantation of 3 .times. 375 mg of progesterone in silicone rubber the concentration rose to 3.8 .+-. 0.51 ng/ml to 48 h and fell steadily to 1.5 ng/ml at 21 days. Removal of the implants caused a reduction to pre-implantation values by 48 h. The increased concentration of circulating progesterone after implantation had no significant effect on the concentration of glucose in plasma, its total entry rate, irreversible loss or on plasma lactate concentration. Glucose recycling increased from 0.13 .+-. 0.05 to 0.38 .+-. 0.12 mg min-1 per kg (P < 0.05). Lactate entry rate fell from 1.68 .+-. 0.16 to 1.12 .+-. 0.10 mg min-1 kg (P < 0.02). The total net formation of lactate from glucose fell from 0.56 .+-. 0.05 to 0.41 .+-. 0.08 mg min-1 kg (P < 0.05). The production of lactate from non-glucose substrates fell from 1.15 .+-. 0.11 to 0.70 .+-. 0.04 mg min-1 per kg (P < 0.02). The utilization of lactate for purposes other than glucose synthesis fell from 1.50 .+-. 0.14 to 0.97 .+-. 0.09 mg min-1 kg-1 (P < 0.05). Progesterone apparently produces an increase in glucose recycling by pathways involving compounds other than lactate.