Role of isoprenoids in cytoskeleton integrity and albumin endocytosis by opossum kidney cells.

Background: The actin cytoskeleton has been increasingly implicated in endocytic events that are involved in the reabsorption of filtered protein by the proximal tubule. Isoprenylated small G proteins have emerged as key regulators of the actin cytoskeleton. This study examines the role of isoprenoid intermediates in organization of the cytoskeleton, and the effect of modification of the cytoskeleton on albumin endocytosis.

Effects of rilmenidine on proximal tubular fluid absorption in rats.

The antihypertensive agent rilmenidine has threefold higher affinity for I(1) imidazoline receptors compared with alpha(2)-adrenoceptors and acts on the central nervous system by reducing sympathetic activity and in the kidney by inhibiting Na(+)/H(+) exchange activity. In the present study, we examined: (i) the effects of luminal and peritubular administration of rilmenidine on fluid absorption in superficial proximal tubules; and (ii) the nature of the receptors involved in mediating the action of this drug in the presence of specific antagonists (efaroxan, idazoxan and 2-methoxy-idazoxan). Studies were performed in anaesthetized Sprague-Dawley rats using shrinking split-drop micropuncture.

Increased proximal tubule NHE-3 and H+-ATPase activities in spontaneously hypertensive rats.

Objective: To investigate renal proximal tubular sodium-hydrogen exchanger 3 (NHE-3) and H+-ATPase activities in young (5-week-old) spontaneously hypertensive rats (SHR) and normotensive Donryu (DRY) rats, in the period during which high blood pressure is developing.

Methods: Five-week-old SHR and DRY rats were weighed and systolic blood pressure recorded. Proximal tubule cells were isolated, loaded with the intracellular pH dye, 2'-7'-bis-carboxyethyl-5(6)-carboxyfluorescein-acetoxymethyl-ester and acidified with a NH4+/NH3 prepulse.

Actions of endothelin-1 on cultured rat renomedullary interstitial cells are modulated by nitric oxide.

1. Cultured renomedullary interstitial cells (RMIC) isolated from 4-week-old Sprague-Dawley rat kidneys possess ETA receptors, as identified by reverse transcription-polymerase chain reaction (RT-PCR). 2.

Inhibition of proximal tubular fluid absorption by nitric oxide and atrial natriuretic peptide in rat kidney.

Atrial natriuretic factor (ANF) and nitric oxide (NO) stimulate production of guanosine 3',5'-cyclic monophosphate (cGMP) and are natriuretic. Split-drop micropuncture was performed on anesthetized rats to determine the effects of ANF and the NO donor sodium nitroprusside (SNP) on proximal tubular fluid absorption rate (Jva). Compared with control solutions, SNP (10(-4) M) decreased Jva by 23% when administered luminally and by 35% when added to the peritubular perfusate.