Reduction of adrenaline-dependent lipolysis in the adipose tissue of adrenalectomized dogs by an alpha adrenergic effect]

In dog, surrenalectomy reduces isoprenalino-depending lipolysis but still more adrenalino-depending lipolysis. Phentolamine potentializes the response to adrenaline but does not that observed with isoprenaline. Surrenalectomy unmasks an alpha adrenergical effect of adrenaline on adipocytes of dog adipose tissue.     

Plasma vasopressin during increases and decreases in blood volume in anaesthetized dogs

In chloralose-anaesthetized dogs, plasma vasopressin concentration was measured by radioimmunoassay during step changes in blood volume of 4 mL/kg over a range of blood volume from +20 to -12 mL/kg. Blood volume was both increased and decreased over this range. There was a logarithmic relationship between blood volume and plasma vasopressin concentration over the range of blood volume examined. There was also a logarithmic relationship between blood volume and mean left atrial pressure. Linear regression between the natural logarithm of plasma vasopressin concentration and mean arterial pressure, heart rate, and mean left atrial pressure gave the highest correlation coefficient (r = 0.94) between vasopressin and mean arterial pressure. The results support the hypothesis that there are sensitive mechanisms controlling the release of vasopressin in response to changes in blood volume. Observations were also made of changes in atrial pressure and activity of left atrial receptors during changes in blood volume over the same range. The results suggest that changes in atrial receptor activity are unlikely to be the major cause of the large increases in plasma vasopressin concentration associated with hypovolemia.     

Adrenal catecholamine synthesis rate changes induced by combined thermal and immobilization stress in fed and 24 hour fasted rats

The combined stress of acute immobilization (IM) at high and low ambient temperature has been used to determine its influence on adrenal catecholamine (CA) content assassed histofluorimetrically in fed and 24 hour fasted rats. The general course of changes obtained after the arrangement of adrenal strips deriving from the adrenals of rats exposed to cold and IM stress (CIMS) at +10 degrees C to -25 degrees C during the different time fragments presented the adrenal CA depletion events followed sometimes by the adrenal CA content increase after the longer stress exposure or/and stronger CIMS and WIMS conditions. It was found that this depletion-stimulated increase of adrenal Ca synthesis rate had been accelerated in 24 h fasted rats compared to satiated ones exposed to the same stress conditions, especially after the CIMS exposure. Moreover the survival time duration at first lethal temperature (-5 degrees C and +45 degrees C) was significantly higher in fasted rats. The possible hypothalamic regulation of adrenal CA synthesis rate accordingly to the actual metabolism needs and beta-adrenoceptor sensitivity changes depending on satiety state have been discussed and the necessity of further investigations concerning the specificity of stress-induced metabolism changes in 24 h starved rats has been suggested.