Inhibition of vasopressin-release during developing hypernatremia and plasma hyperosmolality: an effect of intracerebroventricular glycerol

In non-hydrated goats prolonged (3 h, 0.02 ml/min) intracerebroventricular (IVT) infusion of 0.35 M glycerol depressed the plasma vasopressin level during the entire infusion period which resulted in a conspicuous water diuresis outlasting the infusion by about 20 min. Since no compensatory drinking occurred during this sustained water diuresis it gradually induced pronounced dehydration (loss of greater than 1 liter of total body water causing 5% increase in plasma [Na+] and osmolality). The same degree of dehydration was in other experiments induced by water deprivation. It then caused a 5-fold increase in plasma vasopressin level. Corresponding IVT infusions of 0.35 M d-glucose depressed plasma vasopressin level only during the first half of the 3 h infusion period. Consequently, the resulting water diuresis was transient and subsided before the glucose infusion was finished. Plasma renin activity increased during the IVT glycerol infusion and during water deprivation, but was largely unaffected by IVT glucose. Both IVT glycerol and glucose decreased renal sodium excretion. The possibility is discussed that the pronounced ability of IVT glycerol to depress the vasopressin release and thirst is not only due to dilution induced reduction of CSF [Na+], but also to an influence of glycerol on choroidal and/or transependymal Na+-transporting mechanisms.

1H-N.M.R., 13C-N.M.R., and mass spectra of glucosinolates and related compounds

The mass spectra of per(trimethylsilyl) ethers of desulfated glucosinolates are dominated by ions derived from the glucose moiety. The ions at m/e 271 and 361 are much more abundant than in the spectra shown by the corresponding derivatives of hexoses and their simple glycosides. The individual glucosinolates are distinguished by a few ions originating from their respective aglycon groups. The 1H- and 13C-n.m.r. spectra of sinigrin and some closely related compounds have been analyzed.

Intracerebroventricular glycerol: a potent inhibitor of ADH-release and thirst

Infusions of isotonic or hypertonic (0.3 or 0.5 M) glycerol into the lateral cerebral ventricle (60 min, 0.02 ml/min) of non-hydrated goats invariably induced a conspicuous and sustained water diuresis. Corresponding infusions of 0.3 M glycerol/0.16 M NaCl were almost equally efficient in this respect. A more short-lasting and less pronounced water diuresis was obtained in response to equivalent infusions of pure d-glucose, and the response to 0.3 M glucose/0.16 M NaCl was variable. Intravenous injections of vasopressin blocked the glucose-induced diuresis, but only postponed the glycerol-induced diuresis. Intracerebroventricular (IVT) infusions of 0.5 M glycerol caused a sustained, complete inhibition of the urge to drink in the 48 h dehydrated goat, whereas IVT glucose only attenuated dehydrative drinking. Twenty min after the infusions of glycerol the CSF [Na+] in the lateral ventricle was about 15% below normal. About 10% reduction of CSF [Na+] was obtained 20 min after the IVT infusion of glycerol/NaCl. The corresponding infusion of pure d-glucose reduced the CSF [Na+] by less than 5%. The glycerol and glycerol/NaCl infusions caused a moderate reduction of renal Na+ + K+ excretion. The possibility is discussed that the observed effects of IVT glycerol is a manifestation of its efficiency to inhibit choroidal and/or juxtaventricular (Na+-K+)-ATPase activity.

Influence of altered CSF solute composition on parotid salivary secretion in goats

Infusions of hypertonic NaCl solution into the CSF of the lateral cerebral ventricle of the goat caused a marked reduction in parotid salivary flow concomitant with a rise in salivary [Na+]. Corresponding infusions of iso- or hypertonic glucose and glycerol solutions affected salivary secretion in the opposite direction. The possibility is discussed that a periventricular sodium-sensitive mechanism, which is of importance in the central control of fluid balance, also may participate in the regulation of parotid secretion in the goat. This interpretation of the results is to some extent obscured by the observation of a high incidence of intermittent rumination during the intraventricular infusions of glucose and glycerol solution.

Inefficiency of isoprenaline to induce drinking in the goat

Isoprenaline, which acts as a potent dipsogen in water-satiated rats and dogs, did not elicit water intake when infused intravenously at 0.1 or 0.3 mu/kg min-1 in non-hydrated goats. Even the low dose of the drug caused a marked reduction of parotid salivary flow. The possibility is discussed that reduced salivary secretion might be the particular effect which makes isoprenaline dipsogenic in prandially drinking species. The intravenous infusion of isoprenaline at the high dose level caused an inhibition of the water diuresis of hydrated goats, concomitant with reduced renal Na+ excretion and a marked, sustained fall in the arterial blood pressure. Significant amounts of ADH were recovered from the urine secreted during the antidiuresis. This ADH-release was apparently not due to central beta-adrenergic stimulation since no inhibition of the water diuresis was observed during intraventricular infusions of isoprenaline. Rather, the ADH-release appears to have been secondary to the isoprenaline-induced fall in arterial blood pressure.

Inhibition of natidiuretic hormone secretion by intracarotid infusions of slightly hypertonic non-electrolyte solutions

Relatively rapid (3.75 ml/min), unilateral intracarotid infusions of slightly hypertonic (0.35 m) galactose and glycerol solutions induced a water diuresis within 40 to 60 min in the non-hydrated goat. The response to equi-osmolal fructose solution was weaker and less consistent. The water diuresis was apparently due to an inhibition of the basic ADH secretion, since it could be inhibited temporarily by the administration of small amounts of arginine vasopressin. The corresponding intracarotid infusion of isotonic NaCl solution did not significantly alter the renal clearance of free water, nor did equivalent intrajugular infusions of the non-electrolyte solutions induce water diuresis.

The results appear incompatible with the osmoreceptor theory, and support the assumption that a central, Na+ sensitive receptor system may be involved in the regulation of the ADH secretion.

Accentuation by angiotensin II of the antidiuretic and dipsogenic responses to intracarotid infusions of NaCl and fructose

Infusions of angiotensin II (angiotensin) into the lateral cerebral ventricle of hydrated goats were made alone, or in combination with intracarotid infusions of hypertonic NaCl. The dose of angiotensin used (0.3 ng/kg min) had negligible antidiuretic, and no dipsogenic effect of its own. However, it markedly potentiated the antidiuretic hormone (ADH) releasing effect of intracarotid infusions of hypertonic NaCl, and made these infusions become dipsogenic.

When angiotensin was infused together with hypertonic NaCl into the carotid artery, a 15 times higher dose had to be administered to obtain a comparable degree of potentiation. The results confirm that Na+ and angiotensin interact in the central control of water balance and support the view that receptors sensitive to changes in the Na+ concentration of the cerebrospinal fluid play a role in this control.

When infused into the carotid artery together with hypertonic fructose, angiotensin also enhanced the ADH-releasing effect of the fructose infusions. If this reflects a central sodium-angiotensin interaction, it would indicate that the intracarotid infusion of hypertonic fructose affects the formation of cerebrospinal fluid in such a manner as to cause a rise in its Na+ concentration.