alpha(1)-adrenoceptors: Subtypes, signaling, and roles in health and disease

alpha(1)-adrenoceptors mediate some of the main actions of the natural cate cholamines, adrenaline, and noradrenaline. They participate in many essenti al physiological processes, such as sympathetic neurotransmission, modulati on of hepatic metabolism, control of vascular tone, cardiac contraction, an d the regulation of smooth muscle activity in the genitourinary system. It is now clear that alpha(1)-adrenoceptors mediate, in addition to immediate effects, longer term actions of catecholamines such as cell growth and prol iferation. In fact, adrenoceptor genes can be considered as protooncogenes. Over the past years, considerable progress has been achieved in the molecul ar characterization of different alpha(1)-adrenoceptor subtypes. Three main subtypes have been characterized pharmacologically and in molecular terms. Splice variants, truncated isoforms, and polymorphisms have also been dete cted. Similarly, it is now clear that these receptors are coupled to severa l classes of G proteins that, therefore, are capable of modulating differen t signaling pathways. In the present article, some of these aspects are reviewed, together with t he distribution of the subtypes in different tissues and some of the known roles of these receptors in health and disease. (C) 2000 IMSS. Published by Elsevier Science Inc.