Effects of Catecholamines and Adrenergic Blockade on Fluid Reabsorption in Isolated Rat Cauda Epididymidis

Abstract

Abstract-The rate of fluid reabsorption in the cauda epididymidis of rat has been measured in vitro.Both adrenaline and isoprenaline produced a prompt, reversible and dose dependent increase in the reabsorption rate. These effects were completely blocked by propranolol.The response to noradrenaline consisted of two components. I n the presence of an alpha blocker, noradrenaline caused an increase, while in the presence of a beta blocker, it produced an inhibition in the rate of fluid reabsorption. The effects of these adrenergic agents were only observed when sodium ions were present in the intraluminal fluid, suggesting that they only affect the Na+-dependent component of fluid reabsorption.The possibility that they may affect the active transport of sodium in the duct was discussed.The effects of these adrenergic agents were inter preted in terms of the presence of alpha and beta receptors in the epithelium of the rat cauda epididymidis.It is now well established that fluid reabsorption takes place along the entire length of the mammalian epididymal duct. A major part of the rete testis fluid is reabsorbed as it flows down the epididymis (1, 2, 3). The mechanism of fluid reabsorption has been studied in isolated duct of rat epididymis in vitro. It was found that 50 % of the fluid reabsorption is secondary to an active transepithelial transport of sodium ions (4, 5). Furthermore this process, like many epididymal functions, is abolished by castration, indicating that the fluid reabsorption process is dependent upon the presence of circulating androgens (6).There is little information on the role of neurotransmitters in the functions of the epididymis, although it has been shown that the cauda epididymidis is heavily innervated by sympathetic and parasympathetic nerves (7,8). In this paper, we report the effects of adrenergic agents and blockers on fluid reabsorption in isolated rat cauda epididymidis.The results were interpreted in terms of the presence of the alpha and beta adrenergic re ceptors in the epididymal epithelium. MATERIALS AND METHODSMale Sprague-Dawley rats weighing between 200-300 g were sacrificed by a blow on the head. The epididymis was quickly removed and placed in cold Kreb's bicarbonate solution.A segment of the cauda epididymidis (about 0.3 cm long) was dissected free of fat and connective tissue and placed on a specially designed platform similar to that used for measuring secretory rate in isolated rat seminiferous tubules (9). Each end was clamped onto the platform, and incisions were made in the duct close to the clamps. The lumen was

Intravesical Ions, Osmolality and pH Influence the Volume Pressure Response in the Normal Rat Bladder, and This Is More Pronounced after DMSO Exposure

“…Since the bladder content can modify both spike activity and blood pressure elevation, the bladder is indeed not exclu sively under central nervous control: across the urothelium the urine composition influences the ion milieu of the lamina propria and furthermore the excitability of local nerves and muscle cells. In comparable epithelia of the toad bladder and the rat epididymis, neurotransmit ters influence transepithelial ion transport [Wood and Tomlinson, 1974;Wong and Yeung, 1978]. Extracellular NaCl-concentration alone is able to modify blood flow [Höper and Kessler, 1979], Blood flow deals with offtransport of absorbed solutes, whereas intravesical pres sures generate hydrostatic forces for the 'blood-urine bar rier' and modify mucosal blood flow.…”