Factors Influencing the Sensitivity of Rats Under Ethanol Anesthesia to Antidiuretic Hormone (ADH)

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Abstract
In the present study an effort has been made to evaluate different factors influencing the sensitivity of ethanol anesthetized rats to ADH. It was found that several factors affect the response to ADH: 1. The injection medium. While no difference in sensitivity to bovine arginine vasopressin (AVP) dissolved in physiological saline or in 0.1% bovine albumin was observed, the injection of 2-4 samples of human blood plasma markedly decreased the sensitivity to subsequently administered AVP. 2. The weight of animals. Rats 40-80 g weight are 2-3 times more responsive than larger rats to the same dose of AVP. 3. The volume injected. A volume of 0.5 ml, containing 10 [mu]U AVP injected into 40-80 g and 1.5 ml injected into 130 180 g animals was found as the upper volume limit which did not markedly interfere with the response to ADH. The same dose of AVP injected in larger volumes, 1 ml in small and 2 ml in larger rats, was much less effective. When different volumes containing the same concentration of 10 [mu]U AVP/ml were injected, it was observed that a volume up to 1.5 ml in small and 2 ml in larger animals elicited the greatest antidiuretic response. Delivery of AVP to the renal arteries via abdominal aorta did not cause a greater antidiuretic response than the same dose injected intravenously. The ultrafiltrate of human plasma containing AVP had the same antidiuretic activity as the original plasma, suggesting the absence of significant protein binding.