Vasopressin-activated calcium-mobilizing (VACM-1) receptor mRNA is present in peripheral organs and the central nervous system of the laboratory rat

The distribution and physiological role of the neuropeptide, arginine vasopressin (AVP), and its three receptor subtypes, V_1a, V_1b and V₂, has been well described. A fourth AVP receptor, VACM-1, was recently discovered and appears to be a member of the cullin gene family. The objective of this research is to characterize VACM-1 receptor mRNA expression in the CNS as well as in various tissues and organs of the laboratory rat. Northern blotting of poly(A) ⁺ RNA from various tissues demonstrated the size of VACM-1 mRNA in the rat is approximately 6.3 kb. RT-PCR indicated the transcript is present in all twelve tissues examined: brainstem, cerebral cortex, cerebellum, hypothalamus, aorta, gastrointestinal tract, heart, kidney medulla, liver, lung, skeletal muscle, and spleen. Quantitative realtime PCR confirmed RT-PCR results that VACM-1 mRNA is in all organs and tissues and expression levels are similar in all tissues examined. The transcript encoding VACM-1, a novel AVP receptor, appears to be ubiquitously expressed in various tissues of the laboratory rat. VACM-1 shares some similarities with both V₁ and V₂ receptors, as it binds AVP analogues that independently recognized either of these receptors. Therefore, many functions ascribed to activation of the previously known AVP receptors could at least in part be mediated by VACM-1.