Effect of cold pressure test and 2-deoxy-D-glucose infusion on plasma renin activity in man

Increased thirst and plasma arginine vasopressin levels during 2-deoxy-D-glucose-induced glucoprivation in humans

Insulin-induced hypoglycemia by unknown mechanism(s) increases plasma arginine vasopressin (AVP) levels in humans. Mechanisms for increased AVP levels during central nervous system glucoprivation were investigated by administering 20-min i.v. infusions of 2-deoxy-d-glucose (50 mg/kg), a competitive inhibitor of glucose utilization, or normal saline (sham), to 24 normal volunteers. Some of the infusions were administered in combination with neuropharmacological blocking agents (placebo). The behavioral, physiological, metabolic, and hormonal correlates of 2-deoxy-d-glucose (2DG)-induced gluco-privation and AVP secretion were studied in a group (n = 5) pretreated for 1 wk with either mazindol (1 mg per os three times per day), a potent norepinephrine and dopamine-reuptake blocker, or placebo. A second group (n = 5) received either propranolol (3 mg/3 min followed by 80 mug/min) or normal saline infusion before and during 2DG administration. With 2DG alone, plasma AVP levels increased from 1.3+/-0.3 pg/ml at base line to a peak of 4.5+/-1.4 pg/ml at 60 min and remained elevated for 150 min. From 30 to 180 min after 2DG administration, the 2DG-infused volunteers increased their water intake in comparison with sham-infused volunteers. Marked increases in epinephrine and slight increases in norepinephrine were associated with increases in plasma glucose and renin activity and decreases in plasma potassium. Plasma sodium and osmolality increased transiently and mean arterial pressure (MAP) fell. These changes, however, were small and inconstant and could not account for the observed increases in thirst and AVP levels. Pretreatment with mazindol prevented the decrease in MAP and the increase in plasma renin activity (PRA) following 2DG infusions without modifying increased thirst, water intake, or AVP responses to glucoprivation. Pretreatment with propranolol effectively blocked beta-adrenoreceptors as evidenced by increased MAP and plasma epinephrine, and abolition of the RPA increases during 2DG-induced glycoprivation, but did not suppress AVP and thirst responses. A cervical cord-sectioned patient lacking descending sympathetic out-flow had a potentiated thirst response to 2DG-induced glucoprivation in the absence of increases in sodium, catecholamines, and PRA. Thus 2DG administration activates mechanisms for increased thirst and AVP which are unrelated to changes in peripheral catecholamines, MAP, PRA, and osmolality.

Cardiac denervation and other multisystem manifestations caused by isolated autonomic neuropathy in a young diabetic patient

A young, diabetic woman suffering from fainting spells, vomiting, and diarrhea is described. Extensive investigations showed total cardiac denervation, orthostatic hypotension, and disturbances in the the pupillary and sudomotor functions, as well as impairment of glucagon secretion during hypoglycemia. These disturbances were found to be caused by autonomic neuropathy. No signs of peripheral neuropathy could be detected. To the best of our knowledge this is the second case of total cardiac denervation due to diabetic neuropathy described in the literature.

On the mechanism of renin release by restraint stress in rats

Restraint causes an increase in plasma renin activity (PRA) which is not affected by pretreatment with dl-propranolo (1 mg/kg IP) or sotalol (15 mg/kg IP). These doses of beta-adrenergic blocking agents are effective in suppressing the stimulation of PRA by isoproterenol. Large doses of dl-propranolol (10 mg/kg IP) and d-propranolol (5 mg/kg IP) attenuate the restraint-induced PRA increase. Adrenal demedullectomy does not affect the PRA response to restraint. Renal denervation blunts the PRA rise due to restraint, but not to direct stimulation by the beta-adrenergic agonist, isoproterenol. It is concluded that the increase in PRA during restraint stress in rats is not solely dependent on an intact renal sympathetic innervation. A significant portion of this stress-induced PRA increase appears to involve a non-adrenergic mechanism.

Hunger in humans induced by 2-deoxy-D-glucose: glucoprivic control of taste preference and food intake

Intracellular glucopenia induced by 2-deoxy-D-glucose (2DG) administration in man produces increased hunger ratings and magnitude estimates of pleasantness for sucrose solutions. Augmented food intake substantiates these changes in affective behavior and relieves experimentally induced hunger. Intracellular glucopenia activates counterregulatory mechanisms to raise plasma glucose concentrations. Inducing hunger experimentally with 2DG provides a useful method for studying appetitive behavior in humans. The neurohumoral control of pituitary hormone release and other hypothalamic functions may be examined after 2DG infusion.

The renal compression syndrome

A clinical example of perirenal compression producing documented renin-mediated hypertension is presented. The pathophysiology of this disorder is discussed as it relates to renin release mechanisms. In the future, recognition of the renal compression syndrome may obviate needless nephrectomies since simple removal of the source of compression should result in the cure of hypertension.