The function of the metanephros of foetal rabbits and pigs

Abstract

The mesonephros of foetal rabbits and pigs does not elaborate a fluid resembling urine (Stanier, 1960), analyses indicating that the fluid found in the bladder when the mesonephros is present resembles a protein-free filtrate of foetal serum. The function of the early definitive kidney (metanephros) has been investigated in a similar way; and since and Widdowson & McCance (1958) suggested that the chorioallantoic membrane may modify the composition of the fluid in the allantoic sac, this fluid has been compared where possible with the metanephric urine. METHODS Animals. Fifteen litters of rabbits at 22 days gestation and eight litters at 27 days gestation were studied (the metanephros is fnnctional by about the 22nd day). Samples of blood from the heart, of fluid from the bladder, and, in the younger litters, of allantoic fluid, were taken from the foetuses as described by Stanier (1960); samples of blood and fluid in the bladder from litter-mates were pooled for analysis.Eleven litters of foetal pigs of 63-67 days gestation and three litters of 90 days gestation were studied. (These ages were chosen because at 67 days the volume of allantoic fluid is about maximal; and at 90 days the allantoic fluid is fast disappearing, so that some individuals of a litter may have none and others may have 200-300 ml.) The uterus was removed within a few minutes of the sow's death, and in most cases samples of the fluids were taken from the foetuses within 60 min of the death of the sow. During this period the uterus was kept warm in an insulated container so that its temperature did not fall below 350 C. The procedure was the same as that described by Stanier (1960) except that samples of bladder fluids from individual foetuses were analysed separately.Chemical estimations. Chloride and urea concentrations were estimated by the procedures already described (Stanier, 1960); total osmolar concentration by the cryoscopic method of Ramsay & Brown (1955); creatinine concentration by the method of Owen, Iggo, Scandrett & Stewart (1954); phosphate on 0-05 ml. samples by the method of Berenblum & Chain (1938); fructose on 0-05 ml. samples by the method of Bacon & Bell (1948). RESULTSThe results from rabbits are shown in Table 1. It was not possible to carry out the whole programme on all three fluids from every litter. The number of figures used for calculating the mean is shown in brackets.

Rates of oxygen consumption and of anaerobic glycolysis in renal cortex and medulla of adult and new‐born rats and guinea‐pigs

“…Thus, in the young rabbit, it takes between 3 and 4 weeks for the high rate of glycolysis of the renal cortex to fall to values found in the adult animal (Whittam, 1961). McCance & Stanier (1960) showed that the rabbit's foetuses, 9 days before term, and foetal pigs of 90 days gestation, excrete a urine which differs in its composition from the animal's own plasma and from the urine of the adult animal: its urea concentration is about three times that of the plasma, while its concentration of chloride (and presumably of sodium) is only half that of the blood serum. Nearly 30 years ago, McCance & Young (1941) demonstrated that the sodium and chloride clearance during the first 2 weeks of life of a baby were only about one fifth of those of adults, and that in the new-born in general the renal tubules reabsorb more of the sodium and chloride from the glomerular filtrate than adults do (McCance & Widdowson, 1953).…”

The acid—base relationships of the foetal fluids of the pig

“…The anatomical relationships and connexions indicate, as has often been suggested, that the sac must act as a receptacle for the fluid secreted by the mesonephros and early metanephros, but the work of Stanier (1960), Crawford & McCance (1960) and McCance & Stanier (1960) indicates that the fluids passing into the sac from the bladder must be greatly modified during their storage there, probably by the chorioallantoic membranes. It still remains to be discovered just how the fluid is created in the early stages of foetal life and how its composition is altered by the active reabsorption of sodium, accompanied by chloride to some extent, and possibly with some simultaneous ionic exchange of sodium for hydrogen and other radicles.…”

Changing Basal and Stimulated Activity of the Renin‐angiotensin System During the Second Half of Gestation in the Anaesthetized Piglet

“…The arterial blood pressure of the pig fetus increases during the second half of gestation (Macdonald, Llanos, Heymann & Rudolph, 1981;Macdonald, Colenbrander & Wensing, 1983) and concurrent with this there is a development in the competence of the kidney to retain electrolytes and water (McCance & Stanier, 1960;Alt, Colenbrander, Forsling & Macdonald, 1982). There is also evidence that the amount of renin in the fetal kidney increases over this period of gestation (Kaplan & Friedman, 1943), and that the plasma renin activity is high in the new-born piglet (Bailie, Derkx & Schalekamp, 1980;Osborn, Hook & Bailie, 1980).…”