Vasomotor Responses in the Growing Antlers of the Reindeer, Rangifer tarandus

Abstract

REINDEER shed their antlers every winter and grow them again during spring and summer. After shedding, the former site of attachment of the antlers becomes covered with skin, and the new antlers soon start to grow. Throughout the growth period the skin covers the antlers, which are richly supplied with blood. Blood vessels are located superficially in the skin and do not penetrate deeper. Only the tips of the antlers grow very rapidly. Growing tips have a soft, pulpous consistency, and there is continuous ossification proximal to the growth zone. When the antlers are fully grown, the skin necroses and is scraped off. The blood vessels thus have a short functioning time, a feature they share with the blood vessels of the placenta, and can be regarded as a “disposable” vascular bed. We know little about the physiology of antler blood vessels: are they under nervous vasomotor control, and do they respond to biogenic amines in a way similar to the skin blood vessels from which they originate ? To answer these questions, we have investigated the vascular responses in the antlers of reindeer.