1. Circulating intermediary metabolite and hormone concentrations were measured at intervals over 24 h in five uraemic patients before starting dialysis and after 3 months' treatment with continuous ambulatory peritoneal dialysis (CAPD) and in 13 non-uraemic normal controls.
2. Fasting and postprandial glucose concentrations were significantly raised in uraemic patients undialysed and on CAPD but 24 h mean (±sem) levels fell from 6.63 ± 0.40 to 6.00 ± 0.26 mmol/l (P < 0.02) after 3 months' dialysis despite peritoneal glucose absorption. Insulin levels were raised in uraemic patients but were unchanged by CAPD.
3. Uraemia was associated with raised levels of the gluconeogenic precursors lactate and alanine and a further rise in fasting and 24 h mean alanine concentrations occurred with CAPD. Fasting total ketone body concentrations were raised in undialysed uraemic patients but concentrations were suppressed throughout the 24 h in CAPD subjects.
4. Fasting triglyceride concentrations were increased in uraemic subjects and mean 24 h levels rose by 30% from 1.55 ± 0.42 mmol/l before dialysis to 2.02 ± 0.59 mmol/l during CAPD. Non-esterified fatty acid concentrations were low in uraemic patients and remained low during CAPD.
5. Undialysed and dialysed uraemic patients displayed raised plasma glucagon concentrations throughout the 24 h, suppression of the normal nocturnal secretion of growth hormone and raised mean cortisol levels, which were 23% (CAPD) to 57% (undialysed) higher than in normal controls.
6. The endocrine and metabolic abnormalities of uraemia are not fully corrected by CAPD. Many of the additional changes observed during CAPD reflect an adaptation to the constant absorption of peritoneal glucose.