THIOSULPHATE CLEARANCE IN PREGNANCY

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Abstract
In pregnancy the avg. thiosulfate clearance is greater than the simultaneously detd. inulin clearance. The difference is more pronounced at low than at high plasma concn. of thiosulfate; the avg. thiosulfate/inulin clearance ratio was 1.4 at plasma concn. of 6-10 mg./100 cc. and about 1 at plasma concn. of 20 mg./lOO cc. This relationship is independent of whether the plasma concn. is falling, rising, or maintained at a constant level by infusion. The clearance ratio is depressed, sometimes below 1, by saturation of the tubules with p-aminohippurate (PAH), and even more markedly (to 0.78 in one instance) by 4[image]-carboxyphenylmethane-sulfonanilide (Carinamide). It is concluded that in pregnant women thiosulfate is excreted in part by the renal tubules by a process which is depressed by PAH and carinamide and that this tubular process is readily overloaded by elevation of the plasma thiosulfate concn. The expts. using carinamide and PAH show that filtered thiosulfate can be reabsorbed by the tubules under certain conditions. Clearance ratios above 1 at low plasma concns. were also observed in women examined post-partum and in three non-pregnant women, where, however, this ratio is somewhat lower at higher plasma concns. In pregnant and non-pregnant dogs the clearance ratio was depressed by carinamide suggesting that tubular excretion of thiosulfate occurs in the dog also.