Health Category - Part 2

Figure 8 summarizes our current hypothesis of the sequence on molecular events that take place at the osteoblast cell mem­brane and lead to rapid 1,25D electrical effects coupled to exo­cytosis. Mechanical strain exerted on the cell surface is the initial natural primary stimulus that activates stretch-activated cation channels (SA-Cat) expressed in osteoblasts. Bones are subjected […]

In excitable cells, Ca2+ channels function as transducers of an electrical signal (action potential) into a chemical signal (exocy- tosis of neurotransmitters). Osteoblasts, however, are non-ex­citable cells, and 1,25D appears to act in lieu of action poten­tials to facilitate the opening of Ca2+ channels, Ca2+ influx, and an immediate exocytotic response. Recently, Cl– channels have […]

Stimulation of phosphorylation pathways in ROS 17/2.8 cells mimics the effect of 1,25D on ion channel activities. There is previous evidence for modulation of L-Ca channels in osteoblasts by cAMP associated with actions of the natural vitamin D metabolite 24,25(OH)2-vitamin D3 and parathyroid hormone. We found that the cell permeant cAMP analog diBucAMP poten­tiates (about […]

Steroids affect in different ways the activity of ion channels pre­sent in the plasma membrane of target cells. Our studies showed for the first time that physiological nanomolar concen­trations of 1,25D increase outward Cl– currents in primary os­teoblasts and osteosarcoma ROS 17/2.8 cells within the first 5 minutes of treatment (see Figure 2A, B). This […]

The study of membrane-initiated, non-genomic actions of steroids in different cell systems has become a rapidly expand­ing field of research in recent years. The idea of steroids exert­ing a rapid effect at the cell membrane level was first formulat­ed by Szego and collaborators several decades ago. However, the majority of our current knowledge on steroid […]

Introduction Vitamin D was discovered originally as an antirachitic agent. The development of new therapies for treatment and pre­vention of bone mass loss depends on a full understanding of the molecular mechanisms by which osteoblasts produce and secrete bone, and how these processes are regulated by hor­mones such as vitamin D. Here I review studies […]

The diagnosis of pHPT is based on the finding of normal/high serum calcium levels inadequately associated to circulating PTH values at the upper limit or higher than normal. The clinical presentation of pHPT is variable, with asymptomatic/ paucisymptomatic normocalcemic cases being now more fre­quent than classic symptomatic cases. The presence of de­pression and abdominal symptoms […]