title: Effect of melatonin on phagocytic activity and intracellular free calcium concentration in testicular macrophages from normal and streptozotocin-induced diabetic rats.
abstract: This study examined the effect of melatonin (MLT) on in vitro phagocytosis of testicular macrophages taken from control and streptozotocin (STZ)-induced diabetic rats and the possible mechanism of its action. The phagocytic activity was measured as a number of latex beads ingested by 100 macrophages (PI, phagocytic index) in consecutive time points of the incubation. Changes in intracellular free calcium level [Ca2+]i in isolated macrophages in vitro were measured with the use of ratio-image fluorescence microscopy (fluorescent dye: Fura2/AM). Phagocytic index in macrophages isolated from healthy rats was 20% higher than in those from diabetic animals. Melatonin in physiological concentration (10(-7) M) significantly (p < 0.05) increased the PI in testicular macrophages from control animals (PI = 68 +/- 5 with MLT compared to PI = 46 +/- 7 without MLT) while no such effect was observed in the cells from diabetic rats (PI = 36 +/- 23 with MLT compared to PI = 31 +/- 11 without MLT). Basal [Ca2+]i was significantly (p < 0.01) higher in macrophages from diabetic rats compared to control. Stimulation of both control and diabetic testicular macrophages with 10(-7) M MLT resulted in a significant (p < 0.05) increase in [Ca2+]i in cells incubated in 2.5 mM calcium solution while no such response was observed in calcium-free Tyrode solution. However, MLT evoked [Ca2+]i response in macrophages isolated from diabetic animals was much lower than in macrophages isolated from age-matched controls and the time needed for maximal response was much longer. Lack of response in calcium-free solution suggests that extracellular calcium may be necessary to trigger MLT response and in its progression.
authors.affiliation: Department of Vertebrate Physiology, Faculty of Biology, Warsaw University, ul. Miecznikowa 1, 02-096 Warsaw, Poland. jpawlak@biol.uw.edu.pl
authors.forename: Joanna
authors.initials: J
authors.lastname: Pawlak
authors.forename: Jaipaul
authors.initials: J
authors.lastname: Singh
authors.forename: Robert W
authors.initials: RW
authors.lastname: Lea
authors.forename: Krystyna
authors.initials: K
authors.lastname: Skwarlo-Sonta
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D005456:Fluorescent Dyes; D016257:Fura-2; D007700:Kinetics; D008264:Macrophages / Q000187:drug effects*; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D008856:Microscopy, Fluorescence; D010587:Phagocytosis / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D013737:Testis / Q000166:cytology*
chemical_list: D005456:Fluorescent Dyes; D008550:Melatonin; D002118:Calcium; D016257:Fura-2