Fig. 5. (A) Change in relative ventricular mass in cold-acclimated rainbow trout induced by phenylhydrazine hydrochloride injections at weeks 0 and 2 (solid line and triangles) compared with sham-injected control fish receiving saline (solid line and circles) and untreated fish (solid line and open circles). The dotted lines represent the recovery periods. Mean values (± s.e.m.) at weeks 0, 4 and 8 represent N=10 fish. ⁺Significant difference (P<0.05) from the pre-treatment control value at week 0, as detected by ANOVA and Dunnett's test. ^*Significant difference (P<0.05) between a time-matched PHZ-treated and sham-injected group, as determined by Student's t-test statistic (P<0.05). (B) A linear relationship exists between wet and dry rM_V, indicating constant water content among treatment groups.