We used a structural analogue of arginine vasopressin (AVP) and investigated the role of AVP in the maintenance of mean arterial pressure (AP) in anesthetized, water-deprived rats. The administration of [1(beta-mercapto-beta,beta-cyclopentamethylene propionic acid) 4-valine-8-D-arginine] vasopressin, d(CH2)5VDAVP, completely inhibited to 30-40 mma Hg rise in AP which normally accompanied the administration of 50 mU exogenous AVP (group 1). Thus, d(CH2)5VDAVP is a specific antagonist of the vascular effects of AVP. d(CH2)5VDAVP failed to significantly alter AP in water diuretic rats (group 3) and was without effect on urine osmolality during water diuresis or antidiuresis. However, bolus injection of d(CH2)5VDAVP into water deprived rats (group 2) prompted an abrupt fall in AP from 112 +/- 4 to 94 +/- 4 mm Hg (P less than 0.001). This fall in AP was transient, with return of AP to 110 +/- 4 mm Hg within 15 minutes. Administration of saralasin, an angiotensin II antagonist, not only prevented the compensation in AP, but also significantly magnified the maximal hypotensive response seen following d(CH2)5VDAVP (group 4). Discontinuing the saralasin allowed AP to return to baseline. Bilateral nephrectomy (group 5) also prevented the return of AP, further implicating endogenous angiotensin II as the specific mediator of the compensation in AP following d(CH2)5VDAVP administration. These studies clearly demonstrate that circulating AVP contributes to the maintenance of AP during water deprivation in the anesthetized rat. When this vascular action of AVP is blocked, angiotensin II assumes major responsibility for blood pressure regulation in the antidiuretic state.
Selective angiography and indicator-dilution curves were employed to illustrate the fuctional anatomy of the collateral circulation in two patients with chronic obstruction of the superior vena cava. In both, clinical and laboratory evidence favored an etiologic diagnosis of histoplasmosis.
In case 1, the transit time via the main collateral venous pathway, which comprised the left superior intercostal, accessory hemiazygos and azygos veins, was found to be a little greater than 25 seconds.
In case 2, the superior vena caval obstruction was incomplete, but there was an associated severe narrowing of the right pulmonary artery. Distortion of the indicator-dilution curves provided evidence for an increased bronchopulmonary anastomotic circulation to the right lung.
These observations illustrate how radiographic and hemodynamic technics may usefully be combined to assess the effects of acquired diseases of the major blood vessels.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.