Fig. 5. Resting cGMP content is reduced in for^s tubules. cGMP content of for^R (unshaded bars) and for^s (grey bars) tubules were assayed (20 per sample) as described. Tubule samples were either untreated or treated with capa-1 (10^-7 mol l^-1) (Kean et al., 2002) for 10 min prior to terminating the reaction. Data are expressed as cGMP content (fmol 20^-1 tubules) mean ± S.E.M., N=4. ^*Statistically significant data between for^R and for^S (P<0.05).