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KMID : 0376219680050010063
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Chonnam Medical Journal
1968 Volume.5 No. 1 p.63 ~ p.73
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Influence of oxytocin and vasopressin on the renal function of the tortoise (Amyda Japonica)
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Abstract
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The existence of oxytocin in the pituitary-gland of cold-blooded animals has been ascertained, but its physiological significance still remains obscure. In this study the action of oxytocin on renal function of the tortoise was investigated, in view of the fact that it has a diuretic action in many species of mammals. The results obtained are summarized as follows:
1. Oxytocin, unlike in other laboratory animals, elicited a profound antidiuretic response in the tortoise (Amyda japonica). Urine flow, excretion of electrolytes, as well as glomerular filtration rate decreased. With 100 mU/kg, i. v. these parameters decreased down to 30-50% of the control levels, and the effect lasted longer than two hours. There was no evidence that tubular functions are affected by oxytocin.
2. Clearance of PAH showed a significant rise following initial drop. But the secondary rise was considered not, to reflect the actual changes of renal plasma flow.
3. Blood pressure responded to oxytocin with a persistent elevation, differing greatly from higher vertebrates. The antidiuretic effect is not related to the action on the blood pressure.
4. The maximum trasport capacity of glucose (TmG), which is indicative of the functioning tubular mass, decreased in proportion to the decrease in filtration. It is evident that oxytocin diminishes the glomerular filtrationrate, not by reducing filtration in each glomerulus but by reducing the number of functioning nephrons.
5. Lysine-vasopressin, antidiuretic hormone in the hog but not found in lower- vertebrates, induced antidiuresis also in this species. The mechanism, however, is entirely different Like oxytocin it induces antidiuresis by shutting off a part of functioning nephrons.
It is suggested that oxytocin might play a role in conserving water.during dehydration in this species.
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