Interaction of vasopressin and prostaglandins in the toad urinary bladder.

Self Cite

A B S T R A C T Calcium ion plays a major regulatory role in many hormone-stimulated systems. To determine the site of calcium's action in the toad urinary bladder, we examined the effect of trifluoperazine, a compound that binds specifically to the calcium binding protein, calmodulin, and thereby prevents activation of enzymes by the calcium-calmodulin complex. 10 ,LM trifluoperazine inhibited vasopressin stimulation of water flow, but did not alter vasopressin's effects on urea permeability or short-circuit current. Trifluoperazine also blocked stimulation of water flow by cyclic AMP and methylisobutylxanthine, implying a "postcyclic AMP" site of action. Consistent with these results, trifluoperazine did not decrease epithelial cyclic AMP content or the cyclic AMP-dependent protein kinase activity ratio. Assay of bladder epithelial supernate demonstrated calmodulin-like activity of 1.5 U/lg protein. Morphologic studies of vasopressintreated bladders revealed that trifluoperazine did not alter the volume density of cytoplasmic microtubules or significantly decrease the number of fusions between cytoplasmic, aggregate-containing, elongated vesicles and the luminal membrane. Nonetheless, the frequency of luminal membrane aggregates, structures that correlate well with luminal membrane water permeability, was decreased by >50%. Thus, trifluoperazine appears to inhibit the movement of intramembranous particle aggregates from the fused intracellular membranes to the luminal membrane, perhaps by blocking an effect ofcalcium on microfilament function.

Section: Discussionsupporting

confidence: 90%

“…Immunoreactive prostaglandin E2 (PGE2) content was determined in duplicate by the immunoassay method of Dray et al (18) using specific antibody supplied by Boehringer Mannheim Biochemicals (Indianapolis, Ind). We have used this method previously (19).…”

Section: Methodsmentioning

confidence: 99%

Effects of trifluoperazine on function and structure of toad urinary bladder. Role of calmodulin vasopressin-stimulation of water permeability.

Levine¹,

Kachadorian²,

Levin³

et al. 1981

Self Cite

“…In other studies with mammalian nephron segments, lino and Imai (25) and Stokes and Kokko (26) found that exogenously applied PGE2 suppressed Na+ transport in isolated rabbit CCT. In both the CCT and in the toad urinary bladder, ADH has also stimulated the endogenous production of PGE2 (27,28). In these two tissues, inhibition of endogenous PGE production with prostaglandin synthetase inhibitors, such as indomethacin or meclofenamate, has increased the rate of sodium transport or the rate of osmotic water permeation (28)(29)(30)(31). For example, Holt and Lechene (31) demonstrated inhibition of ADH-stimulated Na+ transport in isolated rabbit CCT by prostaglandins produced within that tubule.…”

mentioning

confidence: 99%

Interactions among prostaglandin E2, antidiuretic hormone, and cyclic adenosine monophosphate in modulating Cl- absorption in single mouse medullary thick ascending limbs of Henle.

Culpepper¹,

Andreoli²

1983

109

A B S T R A C T This paper describes the inhibitory effect of prostaglandin E2 (PGE2) on antidiuretic hormone (ADH)-stimulated net Cl-absorption and spontaneous transepithelial voltage (Ve) in single medullary thick ascending limbs of Henle (TALH, thick ascending limb; mTALH, medullary segment; cTALH, cortical segment) obtained from mouse kidney. The experimental data indicate that PGE2 reduced the ADHdependent values of net Cl-absorption (Je,', eq cm-2 s-') and Ve (mV) in a dose-dependent manner; that increasing concentrations of peritubular ADH reversed the PGE2-mediated reductions in the ADH-dependent moiety of Ve in the mouse mTALH; that PGE2 had no effect on cyclic AMP-stimulated increments in Ve in the mouse mTALH; and that PGE2 had no In the renal medulla, this process enriches medullary osmolality, thereby contributing to urinary concentrating power (13,14). In certain species, like the mouse, salt absorption (11) and adenyl cyclase activity (15,16) in the water permeability of mammalian collecting ducts.In the isolated mouse mTALH, NaCl absorption involves the coupled entry of Cl-, and possibly K+ (17, 18), to Na+ entry across apical plasma membranes. In other words, Cl-transport in this nephron segment is a secondary active transport process, driven in part by the Na+ gradient between luminal fluid and cell interior (11,17). Conservative NaCl absorption in this nephron segment is enhanced considerably, and in a dose-dependent manner, by ADH, operating through the second messenger cyclic (c)AMP (11). Conversely, conservative NaCl absorption in the mouse mTALH is suppressed significantly by increases in peritubular osmolality independently of transepithelial osmotic pressure gradients (19).The mouse mTALH, like the rabbit cTALH (6, 20) and mTALH (7), behaves as a hybrid epithelium: the mouse mTALH is electrically leaky (11, 17) and rather permeable to Na+ and to 17), yet is virtually water impermeable either in the presence or absence of ADH (9-11). Consequently, as medullary peritubular salt concentrations vary, there occur varying degrees of dissipative NaCl backleak from interstitium to lumen through the paracellular pathway. Thus, for the mouse mTALH, maintenance of diluting power in the presence of varying NaCl concentrations in peritubular media depends, at least in part, on the interplay between ADH and peritubular osmolality in modifying conservative NaCl transport (11, 19). We will argue in this paper that PGE2 represents yet another factor that modulates the latter in the mouse mTALH.In the amphibian urinary bladder, Orloff et al. (21) found that prostaglandins inhibited the hydro6smotic effect of ADH but did not change the response of the epithelium to cAMP. They inferred that prostaglandins had acted at a locus proximal to hormone-dependent accumulation of cAMP within the cell, with little or no discernible prostaglandin action on transport events beyond cAMP accumulation. Based on in vitro studies in the isolated rabbit collecting duct, Grantham and Orloff (22) also suggested that prosta...

“…In the toad urinary bladder and rabbit cortical collecting duct, prostaglandins El and E2 (PGE1) (PGE2)1 inhibit the change in water permeability induced by vasopressin but not by cyclic AMP (11)(12)(13)(14)(15), whereas inhibition of endogenous prostaglandin synthesis by cyclooxygenase inhibitors increases the response to vasopressin in both the toad bladder (18,(16)(17)(18) and mammalian kidney (19,20). Additionally, PGE2 biosynthesis has been demonstrated in the toad bladder (18,21,22), and basal rates of PGE2 production have been considered to influence the subsequent response to vasopressin (22).…”

mentioning

confidence: 99%

Role of prostaglandin E2 in mediating the effects of pH on the hydroosmotic response to vasopressin in the toad urinary bladder.

Forrest¹,

Schneider²,

Goodman³

1982

A B S T R A C T Acidosis inhibits the hydroosmotic response to vasopressin. Since prostaglandins are known to modulate vasopressin-stimulated water flow we investigated the role of endogenous prostaglandin E2(PGE2) production in the pH-dependent response of the toad urinary bladder to vasopressin. Graded acidification of the serosal media resulted in a progressive decline in vasopressin-stimulated water flow from 26.6±0.5 mg/min at pH 8.4 to 1.7±0.6 at pH 6.9. In these bladders basal PGE2 synthesis increased from 5.09±0.51pmol/min per g hemibladder at pH 8.4 to 18.8±2.8 at pH 6.9. The addition of that concentration of PGE2 produced by the bladder at pH 7.4 (4 nM) to bladders at pH 8.4 resulted in 62-71% of the inhibition usually seen at pH 7.4; these data suggest that basal PGE2 production per se and not other products of prostaglandin synthesis or other pH-dependent events is responsible for the effect of acidosis. Preincubation with prostaglandin synthesis inhibitors reversed in major part the effect of serosal acidification on the response to submaximal concentrations of vasopressin and completely abolished the effect of pH on near maximal concentrations of the hormone. An increase in PGE2 synthesis after vasopressin was not seen at any pH. These studies establish that increased basal PGE2 synthesis plays a critical role in the pH dependence of the hydroosmotic response to vaso-