Modulation of rabbit ventricular cell volume and Na+/K+/2Cl- cotransport by cGMP and atrial natriuretic factor.
Previously we showed that atrial natriuretic factor (ANF) decreases cardiac cell volume by inhibiting ion uptake by Na+/K+/2Cl- cotransport. Digital video microscopy was used to study the role of guanosine 3',5'-monophosphate (cGMP) in this process in rabbit ventricular myocytes. Each cell served as its own control, and relative cell volumes (volume(test)/volume(control)) were determined. Exposure to 10 microM 8-bromo-cGMP (8-Br-cGMP) reversibly decreased cell volume to 0.892 +/- 0.007; the ED50 was 0.77 +/- 0.33 microM. Activating guanylate cyclase with 100 microM sodium nitroprusside also decreased cell volume to 0.889 +/- 0.009. In contrast, 8-bromo-adenosine 3',5'-monophosphate (8-Br-AMP; 0.01-100 microM) neither altered cell volume directly nor modified the response to 8-Br-cGMP. The idea that cGMP decreases cell volume by inhibiting Na+/K+/2Cl- cotransport was tested by blocking the cotransporter with 10 microM bumetanide (BUM) and removing the transported ions. After BUM treatment, 10 microM 8-Br-cGMP failed to decrease cell volume. Replacement of Na+ with N-methyl-D-glucamine or Cl- with methanesulfonate also prevented 8-Br-cGMP from shrinking cells. The data suggest that 8-Br-cGMP, like ANF, decreases ventricular cell volume by inhibiting Na+/K+/2Cl-cotransport. Evidence that ANF modulates cell volume via cGMP was also obtained. Pretreatment with 10 microM 8-Br-cGMP prevented the effect of 1 microM ANF on cell volume, and ANF suppressed 8-Br-cGMP-induced cell shrinkage. Inhibiting guanylate cyclase with the quinolinedione LY83583 (10 microM) diminished ANF-induced cell shrinkage, and inhibiting cGMP-specific phosphodiesterase with M&B22948 (Zaprinast; 100 microM) amplified the volume decrease caused by a low dose of ANF (0.01 microM) approximately fivefold. In contrast, neither 100 microM 8-Br-cAMP nor 50 microM forskolin affected the response to ANF. The effects of ANF, LY83583, and M&B29948 on cGMP levels in isolated ventricular myocytes were confirmed by 125I-cGMP radioimmunoassay. These data argue that ANF shrinks cardiac cells by increasing intracellular cGMP, thereby inhibiting Na+/K+/2Cl- cotransport. Basal cGMP levels also appear to modulate cell volume.
Department of Physiology, Medical College of Virginia, Richmond 23298-0551.
H F
HF
Clemo
J J
JJ
Feher
C M
CM
Baumgarten
D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000037:antagonists & inhibitors / Q000378:metabolism; D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000502:physiology*; D002712:Chlorides / Q000378:metabolism*; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D006162:Guanylate Cyclase / Q000378:metabolism; D066298:In Vitro Techniques; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D011688:Purinones / Q000494:pharmacology; D011817:Rabbits; D013189:SRS-A / Q000037:antagonists & inhibitors; D015290:Second Messenger Systems / Q000502:physiology; D012964:Sodium / Q000378:metabolism*
D000634:Aminoquinolines; D002712:Chlorides; D011688:Purinones; D013189:SRS-A; C016276:8-bromocyclic GMP; D009320:Atrial Natriuretic Factor; C041715:6-anilino-5,8-quinolinedione; D012964:Sodium; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D006162:Guanylate Cyclase; C011145:zaprinast; D006152:Cyclic GMP; D011188:Potassium