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Purines can modify ciliary epithelial secretion of aqueous humor into the eye. The source of the purinergic agonists acting in the ciliary epithelium, as in many epithelial tissues, is unknown. We found that the fluorescent ATP marker quinacrine stained rabbit and bovine ciliary epithelia but not the nerve fibers in the ciliary bodies. Cultured bovine(More)
Hypertonicity of the mucosal bathing medium increases the electrical conductance of toad urinary bladder by osmotic distension of the epithelial “tight” or limiting junctions. However, toad urine is not normally hypertonic to plasma. In this study, the transmural osmotic gradient was varied strictly within the physiologic range; initially hypotonic mucosal(More)
Vasopressin increases the net transport of sodium across the isolated urinary bladder of the toad by increasing the mobility of sodium ion within the tissue. This change is reflected in a decreased DC resistance of the bladder; identification of the permeability barrier which is affected localizes the site of action of vasopressin on sodium transport. Cells(More)
Our guiding hypothesis is that ecto-enzymatic conversion of extracellular ATP to adenosine activates A(1) adenosine receptors, reducing resistance to aqueous humor outflow and intraocular pressure. The initial step in this purinergic regulation is ATP release from outflow-pathway cells by mechanisms unknown. We measured similar ATP release from human(More)
Vasopressin stimulates Na+ transport across toad bladder largely or entirely by decreasing the resistance to Na+ entry into the transporting epithelial cells. Therefore, the hormone should induce proportional changes in short circuit current (I S ) and tissue conductance; the ratio of these changes should equal the driving force (E Na) of the Na+ pump.(More)
  • M M Civan
  • 1978
The intracellular contents of Na+ and K+ appear to modulate a variety of cellular and tissue functions, including transepithelial transport. However these total ionic contents appear to consist of heterogeneous populations of Na+ and K+. No more than a few percent of intracellular Na+ and K+ appear bound. Thus, the heterogeneity of the intracellular ionic(More)
1. The contraction kinetics of single striated muscle fibres and small fibre bundles from the frog and the toad were measured when the load was changed from P(0) to L < P(0). Simultaneous recordings were made of displacement at one end and force at the other end of the preparation.2. After the load was changed, the contractile force generally reached a(More)
Enzymatically prepared split frog skins consisted purely of epithelial cells. Electrical parameters and the cell contents of ATP, ADP, phosphocreatine (PCr), creatine, inorganic phosphate, protein, and water were measured in skins maintained at room temperature. Studies were conducted under base-line conditions, 15 and 60 min after adding vasopressin, and(More)
The volume of certain subpopulations of trabecular meshwork (TM) cells may modify outflow resistance of aqueous humor, thereby altering intraocular pressure. This study examines the contribution that Na+/H+, Cl-/HCO exchange, and K+-Cl- efflux mechanisms have on the volume of TM cells. Volume, Cl- currents, and intracellular Ca2+ activity of cultured human(More)