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In order to have a model for studying the possible implications of 2-ethylhexyl-phthalate and dialysate on connective tissue, we evaluated their direct effects on the air pouch lining tissue and on fibroblast cultures. Air pouches were formed on the backs of 60 ten-week-old Wistar rats by subcutaneous injections of 10 ml sterile air. On the tenth day 2 ml sterile air, or 2 ml 5μg/L or 2 ml 10 μg/L 2-ethylhexyl-phthalate in olive oil, or 2 ml olive oil alone, or 2 ml 5 mg/ml or 12 mg/ml lyophilized dialysate were injected into the air pouches. After sampling at seven or twenty-one days, the rats were killed. The biochemical data showed an increase in sulphated glycosaminoglycans with 2-ethylhexyl-phthalate and dialysate. Electron microscopy findings revealed cellular alterations such as vacuolation and cell remnants with 2-ethylhexyl-phthalate, while the cells of the air pouches treated with dialysate showed regular organelles with increased and dilated cisternae of rough endoplasmic reticulum. Moreover, an increase in collagen fibres surrounding the damaged zones was noticed in 2-ethylhexyl-phthalate and dialysate treated rats. The glycosaminoglycan modifications and collagen fibre increase seem to suggest that the morfological changes, with the features of fibrosis, could be the result of 2-ethylhexyl-phthalate and dialysate action on connective tissue. Moreover, the air pouch technique can be considered a good model for studying the direct effects of 2-ethylhexyl-phthalate and other substances, such as uremic toxins, on connective tissue.

We have isolated peak II, which is the peak of the middle molecules containing polyamines, from dialysate of uremic patients in recirculating dialysis. We investigated the effect of total dialysate, chromatographic peaks, I, II, III, IV and commercial polyamines on polymorphonuclear leukocyte chemotaxis and superoxide production (i.e. phagocytic activity) in healthy and uremic patients. Polymorphonuclear chemotaxis was inhibited by total dialysate and peak II but not by polyamines; polyamines, total dialysate and peak II had no activity on polymorphonuclear phagocytosis.

We studied the ornithine decarboxylase (ODC) activity and polyamines (PAs) content in the red cells lysate before and after haemodialysis of 15 uremic patients and 15 healthy subjects. ODC activity is significantly increased after haemodialysis but the PAs concentrations (particularly spermine and spermidine) do not increase. This could be because of a minimal loss of PAs surplus production. On the contrary the increase of ODC activity could be explained in several ways, e.g. by stimuli during haemodialysis (hypoxia of the first hour of treatment, decrease of plasmatic osmolarity and biological stimulation of the blood during its passage through the filter).

The direct effects of D(2-ethylhexyl)phthalate (DEHP), on subcutaneous tissue were studied in the rat, using the air pouch technique. Two ml of DEHP, either undiluted or diluted in olive oil (10 μm/ml), were introduced into a previously created air pouch in the rats. The air pouch was removed and specimens of the lining tissue examined by optical and electron microscopy. The persistence of DEHP for 7 days is sufficient to cause alterations in the tissue. The major histological changes were the destruction of the tissue organization with cytoplasmic and nuclear alterations resulting in apoptotic bodies. The histochemical data showed an increase of sulphated glycosaminoglycans, showing proof of alterations in fibroblast functions. The authors suggest that the hyperplastic-type alteration induced by DEHP may be connected with the sclerosis of the peritoneal membrane described in uremic patients in CAPD. (Int J Artif Organs 1998; 21:87–94)