COMPARISON OF ORAL AND INTRAPERITONEAL IRON SUPPLEMENTATION IN ANEMICRATS - A REEVALUATION OF THE MUCOSAL BLOCK THEORY OF IRON-ABSORPTION

To evaluate the extent to which daily oral Fe supplements may block Fe absorption from a subsequent dose, we compared effects of oral and in traperitoneal (i.p.) Fe supplementation on Fe status in anaemic rats ( haemoglobin (Hb)90 g/l). A ligated duodenal loop technique was used to assess the effects of the Fe supplements administered either orally o r i.p. at different frequencies on Fe absorption from a subsequent tes t dose. Anaemic Sprague-Dawley rats were assigned to seven groups of e ight rats each and received either oral or i.p. Fe supplements for 3 d as follows: (1) 4 mg oral supplement daily (three doses in 3 d); (2) 4 mg oral supplement once (one dose on day 1, low-Fe dose on days 2 an d 3); (3) 12 mg oral supplement once (one dose on day 1, low-Fe dose o n days 2 and 3); (4) 3.2 mg i.p. supplement daily (three doses in 3 d) ; (5) 3.2 mg i.p. supplement once (one dose on day 1); (6) 9.6 mg i.p. supplement once (one dose on day 1); (7) low-Fe diet (control). The e ffectiveness of the supplements in treating Fe deficiency on each of t he two test-factors, i.e. route of administration and frequency of dos e, was assessed by determining Hb-Fe gain and liver-Fe stores after th e 3 d test period. Oral supplementation was as effective as i.p. in im proving the Fe status of the anaemic animals. However, a 15 min absorp tion of a radio-Fe test dose from a ligated loop in i.p.-supplemented groups was significantly higher (11.68 (SD 1.70) %, 17.39 (SD 4.59) %, 16.71 (SD 3.39) %) than in orally supplemented groups (3.24 (SD 1.35) %, 2.45 (SD 1.05) %, 1.80(SD 0.35) %) despite equal body Fe stores. N o significant difference in intestinal Fe absorption efficiency was de tected within the oral groups but those supplemented only once were mo re effective than or as effective as the group receiving daily supplem ents for 3 d in improving Fe status as indicated by Hb-regeneration ef ficiency. We conclude hat ther: is a mucosal block with the administra tion of oral Fe supplements but the extent of this blocking effect dur ing oral Fe supplementation is not as dramatic as currently thought in the context of the poor efficacy of daily Fe supplementation programm es.