Organic osmolytes in inner medulla of Brattleboro rat: effects of ADH and dehydration.
Inner medullary methylamine [glycerophosphorylcholine (GPC) and glycine betaine (betaine)] and polyol [sorbitol and myo-inositol (inositol)] osmolytes were measured in water-restricted and antidiuretic hormone (ADH)-infused Brattleboro (DI) rats. Compared with DI rats allowed water ad libitum, rats dehydrated for 3 days had higher urinary osmolality (Uosmol) (812 vs. 239 mosmol/kgH2O) and plasma osmolality (Posmol) (333 vs. 296 mosmol/kgH2O). Dehydration reduced betaine content (36 vs. 66 nmol/mg protein) but had no significant effect on GPC, sorbitol, or inositol. In separate protocols, DI rats, allowed water ad libitum, were infused for either 3 or 12 days with either ADH in saline (+ADH) or saline alone (-ADH). Compared with -ADH controls, 3- or 12-day ADH-infused rats were antidiuretic (Uosmol, 1,000-1,300 mosmol/kgH2O) but not dehydrated (Posmol, 297-300 mosmol/kgH2O). Three days of ADH infusion caused an increase in GPC (340%), betaine (80%), and sorbitol (248%) but not in inositol. After 12 days of ADH, further increases were observed in GPC (730%) and sorbitol (870%); inositol was also elevated (170%), whereas betaine was unchanged. Consequently, the total osmolyte content was significantly higher in +ADH than in -ADH [449 vs. 256 (3 days) and 778 vs. 199 (12 day) nmol/mg protein], whereas total osmolyte levels in dehydrated and control rats were similar (222 vs. 219 nmol/mg protein).(ABSTRACT TRUNCATED AT 250 WORDS)
Blumenfeld
J D
JD
Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts.
Hebert
S C
SC
Heilig
C W
CW
Balschi
J A
JA
Stromski
M E
ME
Gullans
S R
SR
D000818:Animals; D003681:Dehydration / Q000378:metabolism*; D007260:Infusion Pumps; D007679:Kidney Medulla / Q000378:metabolism*; D009994:Osmolar Concentration; D051381:Rats; D011910:Rats, Brattleboro / Q000378:metabolism*; D011922:Rats, Mutant Strains / Q000378:metabolism*; D013997:Time Factors; D014667:Vasopressins / Q000494:pharmacology*; D014868:Water Deprivation / Q000502:physiology
D014667:Vasopressins