摘要:

The ontogeny of glutamine uptake by jejunal brush border membrane vesicles was studied in suckling and weanling rats and compared with the data obtained from previous studies done on adult rats in our laboratory. Glutamine uptake represented transport into the intravesicular space rather than mere binding into the membrane as evident by osmolality study. The process of glutamine uptake was temperature dependent suggesting a carriermediated process with a pH optimum at 7.0. Glutamine uptake was driven by Na+and K+gradient in both suckling and weanling rats. Both processes exhibited saturation kinetics and were inhibited by other neutral amino acids suggesting the presence of Na+-dependent neutral brush border system and Na+-independent (L)-like system. The Vmaxof Na+-dependent and Na+-independent processes were significantly greater in suckling rats with Vmaxof 4.9 ± 0.36 nmol·mg protein-1.7 s-1compared to weanling rats with Vmaxof 2.4 ± 0.2 nmol·mg protein-1. 7 s-1and adult rats with Vmaxof 0.70 nmol·mg protein-1-7 s-1. The greater Vmaxin suckling rats is also evident when the kinetic parameters are analyzed by subtracting the sodium-dependent uptake values from the sodium-independent values. Vmaxof 1.59 ±0.3 and 0.76 ± 0.01 nmol·mg protein-17 s-1in suckling and weanling rats, respectively, p<0.01. Km values were not different at 2.5 ± 0.6 and 3.5 ± 0.6 mM, respectively). The data suggest that the activity and/ or the number of transporters are greater during the period of active growth and development. We conclude that glutamine transport in brush border membrane vesicles undergoes age-dependent changes with greater maximal capacity to transport glutamine in the suckling period.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

摘要:

Lactoferrin has been identified as a factor in human colostrum that accounts for increased incorporation of thymidine into the DNA in an in vitro rat crypt enterocyte bioassay. We have examined lacatoferrin-stimulated thymidine incorporation by comparing the effects of ironfree lactoferrin (apolactoferrin) with those of iron-saturated lactoferrin (diferric lactoferrin) under conditions that inhibit the transfer of iron between these iron-binding proteins in the bioassay system. In addition, we have compared the dose-response relationships of diferric lactoferrin and apolactoferrin. The results demonstrated that lactoferrin, independent of iron-binding states, promoted the incorporation of thymidine into the DNA of rat crypt enterocytes. These observations suggest a previously unreported nutritional role for lactoferrin that is independent of its iron-binding capacity.

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID

ISSN:0031-3998    

出版商:OVID    

年代:1990

数据来源: OVID