Abstract
In two experiments, food was withheld from male rats beginning at 12:00 p.m. Fasted
rats and fed controls were killed 8, 16 and 24 hours later. Rats were 4 and 6 months
old in experiments 1 and 2, respectively. Fasted rats had lower (P<0.01) serum levels
of LH, FSH and glucose than did fed rats; serum levels were independent of the duration
of the fast. Serum levels of testosterone were not significantly affected by fasting.
Serum levels of glucose and testosterone varied with time of day (hour, P<0.01) and
were highest at 12:00 p.m. and 4:00 a.m. respectively. Fasting had a greater effect
on serum glucose levels in experiment 1 than in experiment 2 (experiment × fasting,
P<0.01), and the pattern of change in FSH levels over time of day differed in the
two experiments (experiment × hour, P<0.01).
Key words
Follicle Stimulating Hormone - Luteinizing Hormone - Testosterone - Serum Glucose
- Fasting - Circadian Rhythm
1 This study was supported by a grant (MA-4454) from the Medical Research Council of
Canada
