CIRCADIAN-RHYTHMS OF SERUM CONCENTRATIONS OF 12 ENZYMES OF CLINICAL INTEREST

A total of 25 apparently healthy adults (13 men and 12 women), 29.5 ye ars (SD = 3.6 years) of age, served as subjects in a 24-h study conduc ted in Barcelona, Spain, in the spring of 1990. The group had a homoge neous pattern of meals, activity, and behavior. Six blood samples were collected at 4-h intervals over a single 24-h period beginning at 10: 00 h. The oral temperature was measured at 2-h intervals to facilitate an independent biological time reference for the local population bei ng studied. The serum concentration of 12 enzymes of clinical interest were measured in each sample: creatine kinase, creatine kinase 2, ala nine aminotransferase, aspartate aminotransferase, gamma-glutamyltrans ferase, alkaline phosphatase, cholinesterase, lactate dehydrogenase, l actate dehydrogenase 1, 5'-nucleotidase, pancreatic alpha-amylase, and triacylglycerol lipase. We supposed that all experimental data obtain ed for a quantity came from a single ''hypothetical subject'' that rep resented the central tendency of the population and then these data we re analyzed for circadian rhythm by single cosinor. A statistically si gnificant circadian rhythm was detected in all quantities studied (p l ess-than-or-equal-to 0.05) except for serum concentrations of pancreat ic alpha-amylase and triacylglycerol lipase. The maximum daily rhythmi c variation was approximately 10% (interval, 6-14%) for all quantities studied except pancreatic alpha-amylase (2.6%). This rhythmic variati on is greater than the analytical variation except for 5'-nucleotidase and pancreatic alpha-amylase. The acrophases for the quantities studi ed (except that of triacylglycerol lipase) coincide with times near th ose of the oral temperature acrophase (18:01 local time). The results of this study will doubtless contribute to further documentation of th e structure of the human circadian timing system and to establishment of time-qualified reference intervals for a defined group of subjects.