[Zinc deficiency in mucoviscidosis]

Extracellular zinc and ATP-gated P2X receptor calcium entry channels: New zinc receptors as physiological sensors and therapeutic targets

In this review, we focus on two attributes of P2X receptor channel function, one essential and one novel. First, we propose that P2X receptors are extracellular sensors as well as receptors and ion channels. In particular, the large extracellular domain (that comprises 70% of the molecular mass of the receptor channel protein) lends itself to be a cellular sensor. Moreover, its exquisite sensitivity to extracellular pH, ionic strength, and multiple ligands evokes the function of a sensor. Second, we propose that P2X receptors are extracellular zinc receptors as well as receptors for nucleotides. We provide novel data in multiple publications and illustrative data in this invited review to suggest that zinc triggers ATP-independent activation of P2X receptor channel function. In this light, P2X receptors are the cellular site of integration between autocrine and paracrine zinc signaling and autocrine and paracrine purinergic signaling. P2X receptors may sense changes in these ligands as well as in extracellular pH and ionic strength and transduce these sensations via calcium and/or sodium entry and changes in membrane potential.

[Acquired zinc deficiency in a breast-fed premature infant]

Symptomatic zinc deficiency can occur in exclusively breast-fed infants. We report a case in a preterm infant.

CASE REPORT

A 3-months-old exclusively breast-fed premature infant presented with peri-orificial and acral eczematoid lesions. Laboratory investigations revealed lowered zinc levels in the infant's serum and in her mother's milk. A rapid healing occurred after oral zinc supplementation.

DISCUSSION

Zinc deficiency in breast-fed infants is a rare disease caused by a low level of zinc in mother's milk. The clinical features resemble those of acrodermatitis enteropathica. Oral zinc supplementation is required until weaning.