title: Diurnal and seasonal variation of cholecystokinin peptides in humans.
abstract: Cholecystokinin (CCK) was determined in plasma obtained from 10 female (aged 23.4+/-SD 2.3 years) and nine male (aged 22.0+/-SD 1.4 years) healthy volunteers. Blood samples were drawn three times (8.00a.m., 12 noon and 8.00a.m.) on each of two sessions, one in the winter (November-December) and one in the summer (April-July). The participants had fasted (and were nicotine-free) since midnight preceding the sampling. A standardized breakfast was served after the first sampling. CCK was determined by radioimmunoassay. The area under the curve 0-24h (AUC)(CCK Winter) was lower than AUC(CCK Summer) (F(1:17)=4.73; P=0.0440) in the whole group of volunteers. On comparing the CCK concentrations within each session, there was an overall difference in winter (F(2:36)=14.81; P<0.0001) as well in summer (F(2:36)=18.39; P<0.0001). Post hoc comparisons yielded a difference between the 8.00a.m. and 12 noon concentrations on the first day in winter (t=-3.96; P=0.0009) as well as in summer (t=-4.64; P=0.0002). The difference between the summer and winter AUCs(CCK) correlated with the difference between AUCs for temperatures in summer and winter (r=0.58; P=0.0089). The correlation was accounted for by the females (r=0.73; P=0.0171). The results are in accord with a diurnal and a seasonal variation of CCK in human plasma.
authors.affiliation: Department of Neuroscience and Locomotion, Psychiatry Section, Faculty of Health Sciences, Linköping University, SE-581 85 Linköping, Sweden.
authors.forename: Kristina
authors.initials: K
authors.lastname: Lundberg
authors.forename: Ann
authors.initials: A
authors.lastname: Josefsson
authors.forename: Conny
authors.initials: C
authors.lastname: Nordin
mesh_terms: D000328:Adult; D002766:Cholecystokinin / Q000097:blood*; D002940:Circadian Rhythm; D004958:Estradiol / Q000097:blood; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D010507:Periodicity; D012016:Reference Values; D012621:Seasons; D013696:Temperature
chemical_list: D004958:Estradiol; D002766:Cholecystokinin; D006854:Hydrocortisone