oxytocin and Uremia

Subcutaneous injection of polyethylene glycol (PEG) solution in rats produces exponential increases in secretion of arginine vasopressin (AVP) and oxytocin (OT) in proportion to the induced plasma volume deficits. Previously, we reported that acute water loads eliminated the neurohypophyseal hormone responses to hypovolemia, whereas hypertonic NaCl potentiated them. The present experiments indicated that AVP and OT secretion after PEG treatment were blunted by prior maintenance of rats on a sodium-deficient diet for 2 days. In contrast, plasma AVP and OT levels after PEG treatment were enhanced by prior adrenalectomy or ligation of the inferior vena cava or by concurrent administration of phentolamine in association with arterial hypotension. AVP and OT responses to hypovolemia were similarly potentiated in rats made uremic by bilateral nephrectomy or by puncturing their bladders. These results parallel previous findings that osmotic dilution and sodium deprivation each enhance the sodium appetite induced by PEG treatment in rats, whereas hyperosmolality, hypotension, and uremia each abolish it. Consequently, they support our previous hypothesis that sodium appetite is inversely related to the activity of hypothalamic oxytocinergic neurons.

Topics: Adrenalectomy; Animals; Appetite; Arginine Vasopressin; Blood Proteins; Blood Volume; Ligation; Male; Oxytocin; Polyethylene Glycols; Rats; Rats, Inbred Strains; Shock; Sodium; Uremia; Vena Cava, Inferior

Topics: Adult; Axons; Creatinine; Humans; Motor Neurons; Neural Conduction; Oxytocin; Peripheral Nervous System Diseases; Peroneal Nerve; Renal Dialysis; Uremia; Uric Acid; Vitamin B 12

The systematic separation of medium-sized biologically active peptides by high-performance liquid chromatography (HPLC) is described. Three steps are involved: first, high-performance sodium dodecyl sulphate (SDS) gel chromatography on a newly developed column. TSK-GEL 2000SW; secondly, ion-pair reversed-phase HPLC using stepwise elution mobile phases containing SDS and tetrabutylammonium phosphate; thirdly, high-performance cation-exchange chromatography on a Partisil SCX column for purification, using stepwise gradient elution with volatile buffers. Removal of SDS was possible in the final step. This systematic method is fast, reproducible and gives excellent separations and recoveries.

Topics: Body Fluids; Chromatography, High Pressure Liquid; Enkephalins; Humans; Oxytocin; Peptides; Time Factors; Uremia