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
Mann (1951, 1954) showed that meso-inositol constituted a major component of the seminal vesicle secretion. Hartree (1957) found that in the seminal plasma of man, pig and rabbit inositol existed mainly in the free form, but a substantial percentage of the total inositol was in a combined form in that of cattle, horse and sheep. The function of meso-inositol in the secretions of the male reproductive tract is obscure. In contrast to fructose, it does not appear to influence the motility or respiration of spermatozoa, nor does it influence fructolysis. Mann (1954) has suggested that it may play a part in the maintenance of the osmotic pressure in the seminal vesicle secretion. Hartree (1957) has postulated that it may be an intermediate in the conversion of glucose to fructose; a formation of inositol from glucose has indeed
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.
Ammonium ions added in large quantity disappear rapidly from the reservoir of the sheep placenta perfused in situ through the umbilical vessels. Ammonium ions are removed from the reservoir of perfused sheep fetal livers of 108–141 days of conceptual age at a rate of at least 1 µmol/min/g liver. The majority appears as urea. There is little or no change in glutamine concentration. Hepatic carbamoylphosphate synthetase I, ornithine transcarbamylase, argininosuccinate synthetase, argininosuccinase and arginase are present, even at 97 days of conceptual age, in adequate amounts to account for the observed urea production. With the exception of arginase, all levels rise with fetal age. The levels in the maternal liver are comparable with those at 106 days of conceptual age. Arginase is high in the younger fetuses, falls progressively with fetal age and is very low in the mother. It is concluded that (a) the perfused placenta is permeable to ammonia and the placenta may be able to clear ammonia from the fetal circulation at a rate comparable with that of fetal liver; (b) the fetal liver converts ammonia to urea at a rate comparable with the urea production of the fetus; (c) there is virtually no glutamine production by the fetal liver; (d) adequate amounts of the enzymes of urea synthesis are present even in the immature fetal liver to account for the total urea production of the fetus, and (e) the anomalously low arginase level in the maternal liver may conserve maternal arginine, and the high levels in the younger fetuses may be related to fetal polyamine production from maternally derived arginine.
SUMMARY From the left adrenal of ten sheep foetuses and four lambs aged from 110 days after conception to 14 days after birth, adrenal venous blood was collected and assayed for cortisol, corticosterone and aldosterone. These steroids were secreted at all ages but the rate of secretion was greatly increased toward term and after birth. The increase coincided with morphological changes in the adrenal gland. At no stage was the rate significantly increased by corticotrophin, and in two young foetuses it was not decreased by dexamethasone. In two foetuses and one lamb, angiotensin II did not increase the rate of secretion of any of the three steroids significantly, and the blood pressure was raised only in the lamb. It is probable that the secretion of the steroids was maximal under the conditions of the experiments.
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)
