Activity remained subdued in domestic credit markets last week.In the local wholesale market, Rentenbank (rated AAA) added A$150 million to the April 2024 line that it opened two weeks earlier. The increase takes the size of the line to $350 million and was priced at 3.5 basis points wider at 97 bps over Commonwealth bonds.ING Bank Australia bought back A$2.101 billion of the $2.4 billion of June and October 2014 government guaranteed bonds it had outstanding.Of the June 2014 bonds, ING bought back $1.1 billion of the $1.2 billion of floating-rate notes and $649.2 million of the $800 million of fixed-rate notes. And $395.3 million of the $400 million of October 2014 fixed-rate notes were acquired.In the structured sector, specialist sub-prime mortgage originator Bluestone launched a NZ$67.8 million sub-prime mortgage-backed bond via the Sapphire V NZ Series 2013-1 Trust. The issue is multi-tranched, with only the Class AA and AB notes having preliminary 'AAAsf' ratings from S&P.The ratings descend sequentially to the BBBsfs for the Class D notes. The Class E and F notes are unrated.