Welsh mountain sheep of known conceptual age (term 148 days) were given a spinal anaesthetic (2 ml 20% procaine). A hind leg artery was catheterized, the foetus was exposed by Caesarian section, allantoic and amniotic fluids were collected and a catheter inserted into a tributary of an umbilical artery. Blood samples were taken within 15 min of anaesthesia. The heparinized plasma was separated immediately in the cold and stored at −15 °C. Luteinizing hormone (LH) and 17β-oestradiol were determined by radioimmunoassay (Naftolin & Corker, 1971) and competitive binding assay (Corker & Exley, 1970). The oestradiol method removes oestrone and oestriol, but 17α-oestradiol would interfere if present in quantities approaching those of 17β-oestradiol. No, or just detectable, LH activity was found in plasma from mothers or from older foetuses (Table 1). Measurable LH was present in the plasma of 10 out of 11 foetuses aged 117 days or less. There was
Arginine administered to the fetal sheep elicits a brisk transient increase in the glucagon concentration of peripheral fetal plasma. Neither direct elevation of the fetal plasma glucose level nor the induction of fetal hypoglycaemia by insulin infusion to the ewe result in significant changes in fetal plasma glucagon concentration over the short term, in the acutely exteriorised preparation. The results suggest that maturation of the various mechanisms stimulating glucagon secretion occurs at different stages of development.
Catheters were implanted into the fetal dorsalis pedis and maternal jugular veins of 6 ewes of 122–130 days gestation age. Fetal plasma arginine vasopressin (AVP) concentrations rose in the last few days before parturition from undetectable levels to values associated with response to minor stress. Similarly, AVP was frequently present in maternal plasma in the last week of gestation but was rarely detected earlier. The levels attained in the mother were somewhat lower than in the fetus.
1. Sheep foetuses over the age range 105‐142 days and maintained on an extracorporeal circuit removed exogenous acetate at 2·0‐4·9 mg/kg.min. 2. Urinary loss of acetate was less than 12·5% of the administered amount. 3. The rate of acetate removal appeared to be unaffected by the addition of glucose to the circuit. The removal of glucose also seemed to be unaffected by the presence of acetate. 4. A decline in the plasma concentration of free fatty acids and ketone bodies was also observed during the perfusion. 5. It is concluded that under these conditions acetate may have accounted for about one half of the oxygen consumption. The contribution of free fatty acids and ketone bodies must have been small. The relevance of these findings to the nutrition of the foetus in utero is discussed.
