In human, aquaporins (AQPs) are expressed in a variety of tissues, and there are currently 13 known types of AQPs: AQP0 through AQP12.1) Several members of the AQP family are expressed in the intestinal tract, and at least 8 types are known to exist there: AQP1, AQP2, AQP3, AQP4, AQP7, AQP8, AQP9, and AQP10. 2-4)The main types expressed in mucosal epithelial cells in the colon are AQP3, AQP4 and AQP8.5) It has been reported that vasoactive intestinal polypeptide (VIP), a gastrointestinal hormone, is the causative agent in Verner-Morrison syndrome, a disease associated with diarrhoea 6) ; that intravenous administration of VIP in healthy adults causes diarrhoea 7) ; that serum VIP concentrations are elevated in rats with colitis 8) ; and that VIP increases mRNA and protein expression levels of AQP3 in HT-29 cells, which are human colonic epithelial cells.9) It has also been reported that following resection of the small bowel in rats, there is an increase in the mRNA expression of AQP3 in the colon as diarrhoea occurs.9) Based on these findings, AQP3 appears to play a particularly important role in water transport in the colon. Despite suggestions of an apparent relationship between the occurrence of diarrhoea and AQP3 expression levels, the manner in which variations in AQP3 expression are related to the mechanism of action of laxatives has yet to be elucidated.It is believed that commonly used osmotic laxatives, such as magnesium sulphate (MgSO 4 ) and magnesium oxide (MgO), induce diarrhoea by causing an increase in the osmotic pressure in the intestinal tract, 10) but no details are known about the relationship between these osmotic laxatives and water transport. In the present study, we investigated the role of AQP3 in the colon on the laxative effect of MgSO 4 , a widely used osmotic laxative. First, rats were administered MgSO 4 , and faecal water content was measured over time as an indicator of diarrhoea. Then, by analyzing the expression level of genes that sharply increase as a result of increased osmotic pressure, we investigated the relationship between diarrhoea and osmotic pressure. Next, protein expression levels of AQP3, AQP4, and AQP8 in the rat colon were analyzed by immunostaining in order to investigate the distribution and intensity of AQP expression. By analyzing the expression of AQP3 in the colons of rats administered MgSO 4 , the relationship between the expression level and the laxative effects of MgSO 4 was then investigated. MATERIALS AND METHODS AnimalsMale Wistar rats (10 weeks old) were purchased from Sankyo Labo Service Corp., Inc. (Tokyo, Japan). Each rat was caged separately and kept at room temperature (24Ϯ1°C) and 55Ϯ5% humidity with 12 h of light (artificial illumination; 08:00-20:00). The present study was conducted in accordance with the Guiding Principles for the Care and Use of Laboratory Animals, as adopted by the Committee on Animal Research at Hoshi University.Treatment Rats were fasted for 18 h before MgSO 4 administration (water provided ad libitum). An aqueous solut...

meso-Helicates [Ni(3)(pzNTR)(6)].4CH(3)CN and [Fe(3)(pzNTR)(6)](ClO(4))(2).CH(3)OH were prepared (HpzNTR stands for N-tert-butyl-alpha-3-pyrazolylnitrone). The former showed antiferromagnetic coupling between neighboring ions with J/k(B) = -28.2(2) K, which can be reasonably interpreted in terms of the superexchange mechanism. On the other hand, the latter exhibited ferromagnetic coupling with J/k(B) = +0.292(8) K between the two terminal S = 5/2 Fe(3+) ions through the intervening diamagnetic Fe(2+) ion. The admixture of low-lying excited states with the ground state stabilizes the ferromagnetically coupled state, like the Prussian blue magnet.