Abstract
These studies were intended to examine the binding and degradation of plasma lipoprotein fractions and the utilization of lipoprotein-bound cholesterol for progesterone production in cultured rat luteal cells. These cells bound [125I]human low density lipoprotein ([125I]iodo-hLDL), [125I]human high density lipoprotein ([125I]iodo-hHDL), and [125]iodorat HDL ([125I] iodo-rHDL) with high affinity. The equilibrium dissociation constants of the binding of labeled rHDL, hHDL, and hLDL were 90.5, 78.3, and 36.8 μg/ml, respectively. All three lipoproteins were also degraded in a concentration-dependent manner, with apparent K(m) values of 18.3, 17.5, and 22.4 μg/ml for rHDL, hHDL, and hLDL, respectively. The degradation of the lipoproteins was inhibited by lysosomotropic agents, transglutaminase inhibitors, and metabolic inhibitors, suggesting that these lipoproteins undergo internalization and lysosomal degradation. In addition, all three lipoproteins also augmented the hCG-stimulated steroidogenesis. When cells were incubated with reconstituted LDL (the cholesterol ester in the LDL was replaced with [3H]cholesteryl linoleate) and the steroids produced identified, incorporation of tritium label in the progesterone fraction was observed in a time- and concentration-dependent manner. The incorporation of tritium into progesterone was increased by hCG and inhibited by an excess of unlabeled LDL in the incubation medium. These results show that the ovarian cells use lipoproteins as a source of cholesterol for steroidogenesis through receptor-mediated uptake and internalization, and the evidence suggests that the lipoproteins are intracellularly degraded.
| Original language | English |
|---|---|
| Pages (from-to) | 1746-1753 |
| Number of pages | 8 |
| Journal | Endocrinology |
| Volume | 112 |
| Issue number | 5 |
| Publication status | Published - 1983 |
| Externally published | Yes |
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ASJC Scopus subject areas
- Endocrinology
- Endocrinology, Diabetes and Metabolism
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Binding, degradation, and utilization of plasma high density and low density lipoproteins for progesterone production in cultured rat luteal cells. / Rajendran, K. G.; Hwang, J.; Menon, K. M J.
In: Endocrinology, Vol. 112, No. 5, 1983, p. 1746-1753.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Binding, degradation, and utilization of plasma high density and low density lipoproteins for progesterone production in cultured rat luteal cells
AU - Rajendran, K. G.
AU - Hwang, J.
AU - Menon, K. M J
PY - 1983
Y1 - 1983
N2 - These studies were intended to examine the binding and degradation of plasma lipoprotein fractions and the utilization of lipoprotein-bound cholesterol for progesterone production in cultured rat luteal cells. These cells bound [125I]human low density lipoprotein ([125I]iodo-hLDL), [125I]human high density lipoprotein ([125I]iodo-hHDL), and [125]iodorat HDL ([125I] iodo-rHDL) with high affinity. The equilibrium dissociation constants of the binding of labeled rHDL, hHDL, and hLDL were 90.5, 78.3, and 36.8 μg/ml, respectively. All three lipoproteins were also degraded in a concentration-dependent manner, with apparent K(m) values of 18.3, 17.5, and 22.4 μg/ml for rHDL, hHDL, and hLDL, respectively. The degradation of the lipoproteins was inhibited by lysosomotropic agents, transglutaminase inhibitors, and metabolic inhibitors, suggesting that these lipoproteins undergo internalization and lysosomal degradation. In addition, all three lipoproteins also augmented the hCG-stimulated steroidogenesis. When cells were incubated with reconstituted LDL (the cholesterol ester in the LDL was replaced with [3H]cholesteryl linoleate) and the steroids produced identified, incorporation of tritium label in the progesterone fraction was observed in a time- and concentration-dependent manner. The incorporation of tritium into progesterone was increased by hCG and inhibited by an excess of unlabeled LDL in the incubation medium. These results show that the ovarian cells use lipoproteins as a source of cholesterol for steroidogenesis through receptor-mediated uptake and internalization, and the evidence suggests that the lipoproteins are intracellularly degraded.
AB - These studies were intended to examine the binding and degradation of plasma lipoprotein fractions and the utilization of lipoprotein-bound cholesterol for progesterone production in cultured rat luteal cells. These cells bound [125I]human low density lipoprotein ([125I]iodo-hLDL), [125I]human high density lipoprotein ([125I]iodo-hHDL), and [125]iodorat HDL ([125I] iodo-rHDL) with high affinity. The equilibrium dissociation constants of the binding of labeled rHDL, hHDL, and hLDL were 90.5, 78.3, and 36.8 μg/ml, respectively. All three lipoproteins were also degraded in a concentration-dependent manner, with apparent K(m) values of 18.3, 17.5, and 22.4 μg/ml for rHDL, hHDL, and hLDL, respectively. The degradation of the lipoproteins was inhibited by lysosomotropic agents, transglutaminase inhibitors, and metabolic inhibitors, suggesting that these lipoproteins undergo internalization and lysosomal degradation. In addition, all three lipoproteins also augmented the hCG-stimulated steroidogenesis. When cells were incubated with reconstituted LDL (the cholesterol ester in the LDL was replaced with [3H]cholesteryl linoleate) and the steroids produced identified, incorporation of tritium label in the progesterone fraction was observed in a time- and concentration-dependent manner. The incorporation of tritium into progesterone was increased by hCG and inhibited by an excess of unlabeled LDL in the incubation medium. These results show that the ovarian cells use lipoproteins as a source of cholesterol for steroidogenesis through receptor-mediated uptake and internalization, and the evidence suggests that the lipoproteins are intracellularly degraded.
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M3 - Article
VL - 112
SP - 1746
EP - 1753
JO - Endocrinology
JF - Endocrinology
SN - 0013-7227
IS - 5
ER -