Biomedical subjects
Publications and source records attributed to B Lichardus.
Antibodies to either AVP or dDAVP were sought in the serum of a patient suffering from diabetes insipidus and treated with Adiuretin (Spofa) to which the patient had become refractory. Neither the antibodies nor the presence of enzymes inactivating LVP was detected in the serum.
The renal osmotic cortico-papillary gradient and those of sodium, potassium and urea have been determined in normal and hypophysectomized hydropaenic rats and in normal and hypophysectomized saline-loaded rats, hypophysectomy having been performed 2 h prior to the kidney excisions (acute hypophysectomy). Saline loading was found to depress the renal cortico-papillary gradients in both the normal and hypophysectomized rats, the decrease being more pronounced in the latter. Since the hypophysectomized rats excreted significantly less sodium than normals it is inferred that the depressed cortico-papillary osmotic gradient need not invariably be the decisive factor promoting renal sodium excretion as has generally been accepted.
Canine kidneys were preserved under hypothermia in Collins' standard solution and the contents of sodium, potassium, and Na+ and K+-ATPase in several parts of these kidneys were followed. Hypothermic preservation in combination with single perfusion by means of Collins' solution without thermic ischemia caused loss of sodium, increase of potassium, and decrease of the total osmotic cortico-papillary gradient of the kidney. No loss of Na+ and K+-ATPase activity occurred under these conditions. The determination of Na+ and K+-ATPase level in the renal tissue turns out to be a rational method to assess the vitality of an organ to be transplanted.
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Dopamine and noradrenaline content in the posterior pituitary were found to be lower in alcohol-loaded unanesthetized rats than in rats thirsting for 72 h. Dopamine content was also found to be lower in anesthetized saline loaded rats in comparison with hydropenic animals. It is concluded that in situations in which an increase of vasopressin release is expected, the posterior pituitary content of catecholamines will also be increased, and vice versa, which might imply their role in the release of vasopressin.
Small doses of vasopressin (200 micronU min-1 kg-1) did not influence the loss of ability of acutely hypophysectomized rats to react by natriuresis to the extracellular fluid volume expansion with saline, inspite of restoring their arterial blood pressure to normal. It is concluded that the level of antidiuretic hormone efficient enough to concentrate urine is not a decisive factor in the homeostatic mechanism promoting the 'volume' natriuresis.
Blood flow was measured by means of 125I-Antipyrin distribution and was found to be increased in the posterior pituitary of conscious rats following water deprivation for 24 h as compared to either normohydrated control or to force hydrated rats (2.86 ml min-1 g-1 vs. 2.36 ml or 2.08 ml, respectively). Other parameters of systemic haemodynamics, blood flow in the brain or in the hypothalamus and in anterior pituitary did not differ in three experimental groups of rats subjected to various water intake. The increased blood flow in the posterior pituitary in dehydrated rats presumably parallels the locally intensified metabolic rats due to the enchanged stimulation of the antidiuretic hormone release.
Partly purified rat neurophysin was tested for its possible natriuretic activity in acutely hypophysectomized saline-loaded rats (hypophysectomized 2 h prior to saline infusion). Such animals were unable to excrete the saline load. When partly purified rat neurophysin was injected i. p. in a dose of 40 microgram per animal (which corresponds to its content in one rat posterior pituitary) before saline loading, the sodium excretion was not different from that found in acutely hypophysectomized animals, but it was significantly lower than in normal saline-loaded rats. It was concluded that any apparent natriuretic effect of rat neurophysin could not be established by the present experiments under the experimental conditions used.
A short-term test to determine renal concentrating ability without any water deprivation has been described. It consists of osmolatity determinations in three onehour urine portions from spontaneous voidings following an intranasal application of 7 microng of the synthetic analogue of vasopressin-DDAVP per 0,5 m2 body surface. The values of maximal urine osmalatity over 900 mosm/Kg H2O following DDAVP are considered normal whereas values under 600 mosm are consistent with impaired renal function. If, however, the maximal urine osmolality is in the so called "uncertain range" i.e. from 600 to 900 mosm, it is advisable to perform in the same patients also the classical concentration test based on a prolonged dehydration (26 h).
Acute hypophysectomy (AH) prevented the increase of the cardiac output, renal cortical blood flow (e.g. the decrease of the renal vascular resistance) and renal sodium excretion during the ECFV expansion. The non-occurrence of natriuresis in AH rats is suggested as being partly in causal relation to the inability to decrease the renal vascular resistance and thus to increase the peritubular hydrostatic pressure.
Acute experiments were performed in thiobarbiturate (Inactin, PROMONTA) anaesthesia in 21 male rats. It was found that the attenuation of the antinatriuretic effect of aldosterone by a spironolactone Aldactone (BOEHRINGER) in a dose of 10 mg per rat in 1 h i.v. enhanced urine (V) and sodium (UNaV) excretion following the extracellular fluid volume expansion (ECFV) with intravenous infusion of saline. Max. V = 81.44 +/- +/- 7.46 mul min-1 was obtained in Aldactone treated rats as compared to 54.95 + 7.24 mul min-1 in controls: UNaV = 9.89 +/- 1.26 muval min-1 vs. 6.17 +/- 0.73 muval min-1, respectively. The urinary Na/K ratio was also significantly higher in the same samples of Aldactone treated rats (6.15 +/- +/- 1.22 vs. 2.68 +/- 0.19). It is concluded that endogenous aldosterone blunts nriuresis induced by the ECFV expansion.
The natriuresis following an i.v. isotonic saline loading corresponding to 10% of body wt. was markedly decreased after acute hypophysectomy, due to lowered urinary sodium concentration, in anaesthetized dogs. A role of the pituitary in such a homeostatic natriuresis is suggested.
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