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Maintenance of Euglycemia Is Impaired in Gluconeogenesis-Inhibited Iron-Deficient Rats at Rest and during Exercise^1,2,

Exercise Physiology Laboratory, Department of Human Biodynamics, University of California, Berkeley, CA 94720 and Department of Pediatrics, School of Medicine, University of California, San Francisco, CA 94143

To evaluate the hypothesis that mild iron deficiency increases dependence upon gluconeogenesis, control and mildly iron-deficient (Hb = 80 ± 2 g/L) rats were injected with mercaptopicolinic acid (MPA), a known inhibitor of gluconeogenesis, or with injection vehicle (sham) and studied at rest or after 30 min of treadmill running (13.4 m/min, 0% grade). Liver glycogen concentration was lower in resting iron-deficient rats than in resting control rats, but iron deficiency did not influence arterial substrates or hormones in sham-treated rats. Glucose and insulin concentrations were less in resting control and iron-deficient MPA-treated rats than in sham-treated animals. However, arterial lactate was greater in resting iron-deficient MPA-treated rats than control MPA-treated animals, and glucagon and epinephrine were greater in resting iron-deficient MPA-treated rats than in iron-deficient sham-treated animals, indicating that gluconeogenesis is more important to maintenance of euglycemia in resting iron-deficient animals than in controls. Moderate exercise stimulated glucose metabolism in iron-deficient rats, as evidenced by the lower arterial glucose and higher arterial lactate when compared with resting iron-deficient rats. However, MPA treatment did not clearly establish differences between iron-deficient and control rats after exercise. Therefore, changes in substrate and hormone concentrations in resting iron-deficient MPA-treated rats indicate that dependence on gluconeogenesis for maintenance of euglycemia is greater at rest with dietary iron deficiency. Furthermore, consistent with previously published results for severely iron-deficient rats, results from the present investigation indicate that dependence on glucose metabolism is greater during moderate exercise in mildly iron-deficient rats.

KEY WORDS: • exercise • blood glucose • rats • iron deficiency • lactate

¹ Supported by NIH grants DK-19577 and DK-13897.

² The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

³ Current address: Department of Physical Education, California State University, Chico, CA 95929-0330.

⁴ To whom correspondence should be addressed.

Manuscript received 23 September 1993. Revision accepted 15 April 1994.