RESUMEN
Calcium (Ca2+) channels are present in non-excitable as well as in excitable cells. In bone cells of the osteoblast lineage, Ca2+ channels play fundamental roles in cellular responses to external stimuli including both mechanical forces and hormonal signals. They are also proposed to modulate paracrine signaling between bone-forming osteoblasts and bone-resorbing osteoclasts at local sites of bone remodeling. Calcium signals are characterized by transient increases in intracellular Ca2+ levels that are associated with activation of intracellular signaling pathways that control cell behavior and phenotype, including patterns of gene expression. Development of Ca2+ signals is a tightly regulated cellular process that involves the concerted actions of plasma membrane and intracellular Ca2+ channels, along with Ca2+ pumps and exchangers. This review summarizes the current state of knowledge concerning the structure, function, and role of Ca2+ channels and Ca2+ signals in bone cells, focusing on the osteoblast.
Asunto(s)
Canales de Calcio/fisiología , Calcio/fisiología , Osteoblastos/fisiología , Huesos/química , Huesos/citología , Huesos/fisiología , Membrana Celular/química , Membrana Celular/fisiología , Humanos , Osteoblastos/química , Osteoblastos/citología , Transducción de SeñalRESUMEN
Adipocyte lipid metabolism is primarily regulated by insulin and the catecholamines norepinephrine and epinephrine. Stimulation of the beta-adrenergic receptors (beta-AR) by catecholamines causes an increase in the rates of adipocyte lipid degradation and a decrease in the rates of lipid synthesis. These catabolic effects are in opposition to insulin, which causes net anabolic effects. Because most of the postnatal development of adipose tissue mass in pigs results from hypertrophy of adipocytes (rapid in first few weeks of life) caused by increased net synthesis of triacylglycerol, there is interest in the modulation of beta-AR in adipocytes of growing pigs. The beta-AR are characterized by measuring ligand binding to the receptor to ascertain the affinity of the ligand for the receptor and the receptor number. We found the affinity of the receptor did not vary with animal age (10, 28, and 75 d), with adipose tissue depot site, or in adipocytes of protein-deficient pigs. The beta-AR in obese pigs tended to have greater affinity than those in crossbred pigs of the same age and weight. The beta-AR number was not different when expressed per milligram of adipocyte membrane protein in pigs of different age, in obesity, in different adipose tissue depots, or during protein deficiency. The number expressed per cell or per unit adipocyte surface area did not differ between depots or during protein deficiency. The number per cell tended to be greater in the larger cells from 75-d-old pigs than in the smaller cells from 10- and 28-d pigs. It was greatest in obese pigs with the largest adipocytes. Under the various experimental conditions (age, obesity, depot, protein deficiency), the membrane fatty acid composition was greatly different, but in most cases there was no modulation of beta-AR affinity.
Asunto(s)
Adipocitos/química , Envejecimiento/fisiología , Deficiencia de Proteína/veterinaria , Receptores Adrenérgicos beta/análisis , Enfermedades de los Porcinos/fisiopatología , Porcinos/fisiología , Adipocitos/fisiología , Adipocitos/ultraestructura , Animales , Membrana Celular/química , Membrana Celular/fisiología , Membrana Celular/ultraestructura , Dieta con Restricción de Proteínas/efectos adversos , Dieta con Restricción de Proteínas/veterinaria , Ácidos Grasos/análisis , Femenino , Metabolismo de los Lípidos , Lípidos/análisis , Lipólisis/fisiología , Masculino , Obesidad/fisiopatología , Obesidad/veterinaria , Deficiencia de Proteína/fisiopatología , Receptores Adrenérgicos beta/efectos de los fármacos , Receptores Adrenérgicos beta/fisiología , Porcinos/metabolismo , Triglicéridos/análisisRESUMEN
Primary cultures of stromal-vascular (S-V) cells from adipose tissue of new-born pigs were used to evaluate the characteristics of four sera obtained from male and female genetically lean or obese pigs weighing 50-60 kg. (2) Lean pig sera (LPS) stimulated greater levels of sn-glycerol-3-phosphate dehydrogenase (GPDH) activity in cultured cells than obese sera (OPS). Male LPS tended to promote higher GPDH specific activity than female LPS or male and female OPS. When GPDH was expressed on a per DNA basis, male LPS significantly (P < 0.05) increased GPDH per unit DNA compared with female LPS or male and female OPS.
Asunto(s)
Adipocitos/citología , Obesidad/sangre , Células del Estroma/citología , Animales , Diferenciación Celular/fisiología , Células Cultivadas/química , Células Cultivadas/citología , Células Cultivadas/enzimología , ADN/análisis , Femenino , Genotipo , Glicerolfosfato Deshidrogenasa/metabolismo , Masculino , Proteínas/análisis , Factores Sexuales , Células del Estroma/química , Células del Estroma/enzimología , PorcinosRESUMEN
Stromal-vascular (S-V) cells isolated from adipose tissue of newborn pigs (NBPC) and mature pigs (MPC) by collagenase digestion were used to evaluate differences in preadipocyte culture and development. Cells were seeded at a density of 3 x 10(4) cells/cm2 on six-well (35-mm) tissue culture plates in 3 mL of DMEM/HAM's F12 medium plus 10% fetal calf serum and cultured at 37 degrees C under a humidified atmosphere of 95% air:5% CO2 for 24 h. Cells were then washed thoroughly in DMEM/HAM's F12 medium without fetal calf serum and maintained in serum free (SF) medium or SF medium supplemented with 2.5% newborn pig serum (NBPS) or mature pig serum (MPS) for 12 d. After 1 d, more NBPC adhered to the culture plates, as indicated by DNA values. After 12 d, protein per culture well was not significantly different, but DNA concentration per well remained higher (P < .05) in cultures of NBPC than in the MPC cultured in the same medium, indicating fewer MPC. Protein:DNA ratios were higher (P < .05) in cultures of MPC regardless of the medium, reflecting larger cell size. More cells containing fat deposits were seen with NBPC in all conditions in comparison with MPC, and more fat was deposited in NBPC in SF than in SF plus NBPS or MPS. The NBPC had higher (P < .05) sn-glycerol-3-phosphate dehydrogenase (GPDH; EC 1.1.1.8) per protein than MPC regardless of the medium. For both cell types, GPDH activity in either serum was less than activity of cells grown in SF.(ABSTRACT TRUNCATED AT 250 WORDS)
Asunto(s)
Adipocitos/citología , Envejecimiento/fisiología , Adipocitos/química , Adipocitos/fisiología , Animales , Recuento de Células/veterinaria , Diferenciación Celular/fisiología , División Celular/fisiología , Células Cultivadas , ADN/análisis , Masculino , Células del Estroma/química , Células del Estroma/citología , Células del Estroma/fisiologíaRESUMEN
Cimaterol, a catecholamine analog that acts as a beta-adrenergic agonist, has been shown to have a growth promoting effect in rabbits. Catecholamines are also known to stimulate ion transport in many tissues. The objective of this study was to determine the effect of dietary cimaterol on rabbit tissue Na(+)-K+ ATPase activity. Twelve New Zealand White rabbits, fed either control diet or cimaterol-supplemented diet, were killed at the end of a 35-d feeding trial. Heart, kidney, and liver were weighed, and total ATPase and Na(+)-K+ ATPase activities of these tissues were determined. Cimaterol did not affect liver and kidney weights, but heart weight was significantly increased. Cimaterol increased both total and Na(+)-K+ ATPase activities in heart and kidney but had no effect in liver. These data indicate that increased dietary energy intake and body energy expenditure in cimaterol-fed animals can be attributed, in part, to elevated Na(+)-K+ ATPase activities in heart and kidney.
Asunto(s)
Etanolaminas/farmacología , Conejos/metabolismo , ATPasa Intercambiadora de Sodio-Potasio/metabolismo , Adenosina Trifosfatasas/metabolismo , Administración Oral , Animales , Transporte Biológico Activo , Dieta , Metabolismo Energético , Etanolaminas/administración & dosificación , Corazón/efectos de los fármacos , Riñón/efectos de los fármacos , Riñón/enzimología , Hígado/efectos de los fármacos , Hígado/enzimología , Miocardio/enzimología , Tamaño de los Órganos/efectos de los fármacos , Distribución Aleatoria , ATPasa Intercambiadora de Sodio-Potasio/efectos de los fármacosRESUMEN
1. Insulin increased basal 2-deoxyglucose uptake in isolated swine adipocytes by 75%. In the absence of insulin, isoproterenol did not inhibit basal 2-deoxyglucose transport. 2. Adenosine deaminase plus isoproterenol or theophylline alone reduced insulin effect by 10 and 40%, respectively. Isoproterenol alone or with 2-chloroadenosine did not inhibit insulin effect on glucose transport activity. 3. Insulin effect was inhibited by isoproterenol in the presence of theophylline but not in the presence of adenosine deaminase. 4. These results suggest that catecholamines do not counter-regulate basal and insulin-stimulated glucose transport in swine adipocytes.