Use of the CgA ELISA kit for determination of human plasma CgA concentrations is applicable to the measurement of canine plasma CgA concentrations. Canine plasma CgA concentrations, along with measurements of plasma cortisol and catecholamine concentrations, correctly reflect insulin-induced hypoglycemic stressed conditions in dogs. Measurement of canine plasma CgA concentrations may provide a useful index for evaluation of an acute stress response.

ABSTRACT. Renal effects of the selective α 2 -adrenoceptor agonist, medetomidine, were investigated in anesthetized dogs. Animals were administered medetomidine 20 and 40 µg/kg intravenously (IV) and 80 µg/kg intramuscularly (IM) or 1 ml of saline IV. Urine and blood samples were collected before and at 30, 60, 90 and 120 min following medetomidine injection. Mean arterial blood pressure (MABP), renal blood flow (RBF), glomerular filtration rate (GFR), urine volume (U v ), urine osmolality (U osm ), free water clearance (C H2O ), fractional clearance of sodium (F Na ), plasma osmolality (P osm ), plasma glucose levels and plasma antidiuretic hormone (ADH) concentrations were measured. The results showed that IV administration of medetomidine initially increased MABP 5-15 min followed by long-lasting decrease. The initial hypertension was not observed after IM administration, which was accompanied by a more profound hypotensive effects. RBF, GFR, U v , C H2O increased after IV injection and decreased after IM. Medetomidine increased FNa and Posm and decreased U osm . Plasma glucose levels initially increased and subsequently decreased. Plasma ADH concentration was decreased by IV injection but increased by IM administration. Our data imply that: 1) IV administration of medetomidine at dose rates of 20 and 40 µg/kg results in profound diuresis up to 2 hr; 2) Suppression of ADH release from the CNS is one of the mechanisms of medetomidine-induced diuresis although it may not be the principal one. KEY WORDS: anesthesia, canine, isoflurane, medetomidine and renal function.

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