Relation between acute changes in diuresis and renal prostaglandins. II. Induced antidiuresis

We have evaluated the effects of indomethacin (I) and of a rich in linoleic acid phosphatidylcholine (E) on the renal function during in bolo infusion of lysine-8-vasopressin (LVP). 5 normal subjects have been studied in the absence of treatment (TA) and after treatment with I, E, E+I respectively. Two clearance (cl.) periods have been performed in the following time intervals: 0-30 min and 30-60 min after in bolo LVP (1.5 m-U.kg-1) infusion. Have been measured: the urinary flow rate, V, the endogenous creatinine cl., Cc, the osmotic clearances, Cosm, CH2O, the sodium and potassium cl., CNa, CK, the urinary prostaglandins (PG) of E series excretion (UPGV) by RIA method and the mean of arterial pressure (PA). 1) In TA condition LVP decreases V, Cosm, Cc, CH2O, CNa, CK and slightly increases the urinary osmolarity; these effects regress during the interval 30-60 min. 2) In I condition LVP produces a significant increment of PA and prolonged and intensified decrement of Cc, CH2O, V; in this condition the increase of urinary osmolarity is greater than in TA condition. 3) The E-treatment alone does not affect the LVP-induced renal effects; however the enhancement of these effects produced by I is attenuated in the presence of E though UPGV does not differ in I and E+I.     

Role of prostaglandin E2 in regulation of urine excretion in saluresis, water and osmotic diuresis in rat

In the saluresis, water and osmotic diuresis were indicating an increase of prostaglandin E2 excretion and a correlation between this index and diuresis. Unselective blockade of cyclooxygenase by diclofenac-natrium leads to a decrease of diuresis in the observed types of urine-production in rats. Inhibition of inducible cyclooxygenase by celebrex didn't change the value of diuresis after water load or administration of osmotic agent, but decreased the diuretic effect of furosemide.     

Impaired water diuresis in a patient with pseudo-Bartter syndrome.

A 32-year-old man was diagnosed as having pseudo-Bartter syndrome due to surreptitious habitual vomiting and to maldigestion related to decayed teeth. His chief complaints were muscle pain and weakness. In this case, metabolic alkalosis, hypokalemia, hypochloremia, increased plasma renin activity and aldosterone levels were noticed with marked decreases in urinary chloride excretion. Creatinine clearance (GFR) and renal plasma flow (RPF) were also decreased. Blood pressure was normal, but the pressor response to angiotensin II was attenuated. Before treatment with 0.9% saline infusion, plasma vasopressin (AVP) was not suppressed sufficiently by lowering the plasma osmolality (Posm) with an oral water load (WL), but it normally responded to a rise in Posm due to hypertonic saline infusion. Moreover, plasma AVP was normally suppressed by WL after the replenishment of saline. Plasma atrial natriuretic peptide (ANP) was low before WL, but increased normally in response to WL. However, inconsistent with the normal response in this case, decreases in plasma AVP failed to dilute urinary osmolality and to increase urine flow, irrespective of the levels of plasma ANP. These results indicate that chronic inanition due to surreptitious vomiting causes impaired renal diluting ability through decreases in GFR and RPF, irrespective of the levels of plasma AVP and ANP.     

GPC phosphodiesterase and phosphomonoesterase activities of renal cortex and medulla of control, antidiuresis and diuresis rats

Glycerylphosphorylcholine (GPC) concentration was reported to be elevated in renal medulla of experimental animals deprived of water. The activities of GPC phosphodiesterases were similar in homogenates and membrane subfractions of renal cortex prepared from control, diuresis and antidiuresis rats. There were no differences in these preparations' ability to hydrolyze phosphorylcholine. In contrast, there was a nearly 50% reduction of non-specific phosphomonoesterase activity, using p-nitrophenylphosphate as substrate and membrane subfractions prepared from the antidiuresis animals. It is suggested that as a consequence, a pathway for the formation from L-alpha-glycerylphosphate is activated.     

The effect of prolonged immobilization on diuresis and water intake in rats

Diuresis and water intake was determined in 20 male albino rats during 8 weeks of immobilization and in 10 rats in post-immobilization recovery phase. Increase of diuresis and water intake during the immobilization period have been observed. Neither changes in sodium and potassium excretion nor in Na/K ratio were found. As the immobilization of the rats did not cause any changes of their natural body position in relation to the direction of gravity forces, the effect of immobilization on diuresis and water intake could not be related to an ortostatic shift of blood or inhibition of the hypothalamo-hypophyseal antidiuretic system.     

Osmosis: a bimodal theory with implications for symmetry

A theory is advanced that volume transfer across a membrane pore during osmosis takes place in two modes: if solute is sterically excluded from the pore a pressure gradient is set up and viscous flow of solvent results; if solute can enter the pore then osmotic flow is a diffusive phenomenon, and there is no pressure gradient in any part of the pore to which solute has access, even at low concentration due to a repulsive wall field. As a consequence the reflexion coefficients sigma s and sigma f for osmosis and ultrafiltration are not equal, although equality is usually assumed to result from an underlying thermodynamic reciprocity; instead, the two coefficients represent essentially different processes. These results follow from three basic thermodynamic considerations which have usually been overlooked: (i) there is a qualitative difference between a permeable pore and an impermeable one, the latter having a discontinuity of solute activity at the mouth, which the former does not; (ii) the osmotic pressure within the pore is determined by the activity of solute not the concentration; (iii) the effective resistance to flow through a channel depends upon the nature of the régime, being different for diffusive and viscous flow. An expression for sigma s is derived and shown to be compatible with experimental data on polymer membranes and homoporous bilayers.