Effect of chronic intermittent hypobaric hypoxia on relaxation of aorta and mechanisms in developing rats / 中国药理学通报

Aim To investigate the effect of chronic intermittent hypobaric hypoxia (CIHH) on relaxation of thoracic aorta rings in male developing rats and the underlying mechanisms. Methods Male neonatal Spra-gue-Dawlay ( SD) rats were randomly divided into eight groups respectively: CIHH treatment group (CIHH), group of one-week post-CIHH (CIHH-pl), group of two-week post-CIHH ( CIHH-p2 ) , group of three-week post-CIHH (CIHH-p3 ) , control group for CIHH (Con), control group for CIHH-pl (Con-1), control group for CIHH-p2 ( Con-2) and control group for CIHH-p3 (Con-3 ). Rats in CIHH groups were put into a hypobaric chamber with the mother rats 1 ~ 3 days before the birth to get a hypobaric hypoxia exposure mimicking 3 km altitude for 42 days, 5 hours daily. Rats in control groups were kept in the same environment as CIHH rats except hypoxia exposure. After anaesthetized with pentobarbital sodium (50 mg • kg-1 i. p. ), the thorax of rats was opened and thoracic aorta rings were made. The artery rings were placed in the bath chamber filled with K-H solution, and the relaxation of artery rings was recorded under normoxia or a-cute hypoxia conditions, respectively. Results (1) Under normoxia condition, the acetylcholine ( ACh)-induced relaxation of thoracic aorta increased obviously in CIHH groups compared with corresponding Con groups ( P < 0. 05 ). ( 2 ) The enhancing effect of CIHH treatment on thoracic aorta could be maintained for at least three weeks (P < 0. 05). (3 ) Under acute hypoxia condition, ACh-induced relaxation of thoracic aorta in each group decreased obviously, but the decrease in CIHH groups was significant less than that in Con groups ( P < 0.05 ). (4) The enhancement of CIHH on relaxation of thoracic aorta could be reversed by indomethacin (Indo), a cyclooxygenase inhibitor, glibenclamide (Gli), a KATP blocker, and Tempo, a free radical scavenger. Conclusions CIHH augments endothelium-dependent relaxation in thoracic aorta of developing rats. Also, CIHH can antagonize the inhibition of acute hypoxia on relaxation of thoracic aorta. The enhancing effect of CIHH treatment may be related with the increase of prostacyclin, the opening of KATP and free radical production.

Immunocytochemical Study of Calbindin D(28k) Positive Cells in the Developing Rat Kidney / 대한해부학회지

Calbindin D(28k),a calcium binding protein,is found in various tissues,including some cells in the distal nephron.It plays an important role in the regulation of calcium reabsorption. We previously reported the expression of calbindin D(28k) in adult rat kidney.However,the exact time of expression during differentiation in the embryonic kidney is not known.During development,intercalated cells are deleted from the medullary collecting duct by two distinct mechanisms.However,the reason for the different modes of cell death is not known.As calbindin is reported to protect cells against apoptosis,we examined the expression of calbindin D(28k) in the developing rat kidney.Kidneys from 16-,17-,18-and 20-day-old fetuses and 1-,3-,5-,7-,14-and 21-day-old pups and adult Sprague awley rats were processed for immunohistochemistry using a monoclonal antibody against calbindin D(28k) .Intercalated cells were identified by immunostaining for H+ -ATPase and by electron microscopy.Calbindin D(28k) immunoreactivity first appeared in subpopulations of cells in the connecting tubule and medullary collecting duct in the 17-day-old fetus.In the connecting tubule,calbindin D(28k) was expressed only in H+ -ATPase negative connecting tubule cells,and there was no labeling of intercalated cells.In the medullary collecting duct,calbindin D(28k) immunostaining was observed in a few cells with apical H+ -ATPase,characteristic of type A intercalated cells.The numbers of calbindin D(28k) -positive type A intercalated cells increased from day 18 of gestation.In contrast,there was little or no calbindin D(28k) immunoreactivity in the type B intercalated cells or principal cells.During the first two weeks after birth,calbindin D(28k) -positive type A intercalated cells were lost from the terminal part of the medullary collecting duct by simple extrusion. After two weeks,calbindin D(28k) immunostaining decreased in the type A intercalated cells throughout the medullary collecting duct.However,the immunoreactivity of calbindin D(28k) in the cortical collecting duct was increased in some of the type A intercalated cells and the adult pattern was observed in 21-day-old pups.Thus,we propose that the different expression of calbindin D(28k) in type A and type B intercalated cells may be responsible-at least partly-for the different modes of cell death demonstrated in these cells during kidney development.

Developmental Expression of Epidermal Growth Factor in Rat Kidney / 대한해부학회지

Epidermal growth factor (EGF) is well known to be one of regulating factor in proliferation. The aims of the present study were to elucidate the expression time and localization of expression of EGF in developing rat (Sprague-Dawley) kidney. Kidneys of 16-, 18- and 20-day-old fetuses, 1-, 3-. 7-, 14-, and 21-day-old pups and adult (3months) were preserved for light and electron microscopic immunocytochemistry. In adult rat kidney, EGF immunoreactivity was well localized in thick ascending limb and distal convoluted tubule. In developing rat kidney, EGF-positive cells appeared first in cortical thick ascending limbs and distal convoluted tubules of juxtamedullary nephrons at 3 days and 7 days after birth respectively, in cortical thick ascending limbs and distal convoluted tubules of cortical nephrons at 14 days after birth, and in medullary thick ascending at 21 days after birth. These findings suggest that renal EGF synthesized and secreted from distal tubule may possibly accelerate not proliferation but differentiation of the renal tubular epithelium at least in neonatal rat kidney.

Expression of AQP-4 in Developing Rat Stomach: An Immunohistochemical Study

PURPOSE: AQP-4 is restricted to basolateral membranes of parietal cells located in the gastric glandular base. Whereas, there is no AQP-4 immunoreactivity in the parietal cells of isthmus/ neck region of gastric gland. Expression of AQP-4 in parietal cells might be related with the functional differentiation and maturation of parietal cells. The purpose of this study was to establish the expression of AQP-4 in differentiating parietal cells in the developing rat stomach. METHODS: Stomachs from 20-day-old fetuses, 3-, 7-, and 14-day-old pups, and adults were preserved with a periodate-lysine-paraformaldehyde solution and processed for immunohistochemical studies using rabbit polyclonal antibodies to AQP-4 or H+/-K+/-ATPase. RESULTS: In the parietal cells during development of rat stomach, AQP-4 appears first at 20 days of gestation. AQP-4 immunoreactivity is restricted to the basolateral membranes of parietal cells located in the gastric glandular base not only in adults but also in all developing ages. Whereas, there is no AQP-4 immunoreactivity in the parietal cells of isthmus/neck region in all developing ages. CONCLUSION: These results suggest that in the developing rat stomach, AQP-4 expressed only in mature parietal cells which are located in the glandular base, and act as a major water channel involved in acid secretion in rat stomach.